ORCID Profile
0000-0002-9486-2343
Current Organisations
University of Technology Sydney
,
CSIRO
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Microbiology | Microbial Ecology | Microbiology Not Elsewhere Classified | Nanotechnology | Nanotoxicology, Health and Safety | Microbial Genetics | Water Treatment Processes | Environmental Nanotechnology | Food Packaging, Preservation and Safety | Molecular evolution | Chemical Engineering Design | Organic Chemical Synthesis | Powder and Particle Technology | Analytical Spectrometry | Chemical Sciences Not Elsewhere Classified | Environmental Biotechnology not elsewhere classified | Microbiology not elsewhere classified | Microbiology not elsewhere classified | Other Chemical Sciences | Environmental Biotechnology | Geomechanics and Resources Geotechnical Engineering | Bacteriology | Resources Engineering and Extractive Metallurgy | Mining Engineering | Metals and Alloy Materials | Infectious Agents | Microbial ecology | Biomedical Engineering not elsewhere classified | Building Science and Techniques | Analytical Chemistry | Colloid and Surface Chemistry | Biomaterials | Biomedical Engineering | Chemical Engineering | Structural Chemistry and Spectroscopy | Food Sciences | Genetics | Infectious Agents | Medical Biochemistry: Lipids | Plasma Physics; Fusion Plasmas; Electrical Discharges | Bacteriology
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Engineering | Environmental Health | Health Protection and/or Disaster Response | Control of Animal Pests, Diseases and Exotic Species in Coastal and Estuarine Environments | Biological sciences | Land and water management | Coal Mining and Extraction | Industrial Machinery and Equipment | Health not elsewhere classified | Infectious Diseases | Coated Metal and Metal-Coated Products | Plastic products (incl. Construction materials) | Metals (e.g. Composites, Coatings, Bonding) | Workplace Safety | Expanding Knowledge in the Medical and Health Sciences | Expanding Knowledge in Technology | Land and Water Management of environments not elsewhere classified | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Scientific Instruments | Environment not elsewhere classified | Food Safety | Meat products |
Related Links
Publications
Involvement of nitric oxide in biofilm dispersal of Pseudomonas aeruginosa
Publisher: American Society for Microbiology
Date: 11-2006
DOI: 10.1128/JB.00779-06
Abstract: Bacterial biofilms at times undergo regulated and coordinated dispersal events where sessile biofilm cells convert to free-swimming, planktonic bacteria. In the opportunistic pathogen Pseudomonas aeruginosa , we previously observed that dispersal occurs concurrently with three interrelated processes within mature biofilms: (i) production of oxidative or nitrosative stress-inducing molecules inside biofilm structures, (ii) bacteriophage induction, and (iii) cell lysis. Here we examine whether specific reactive oxygen or nitrogen intermediates play a role in cell dispersal from P. aeruginosa biofilms. We demonstrate the involvement of anaerobic respiration processes in P. aeruginosa biofilm dispersal and show that nitric oxide (NO), used widely as a signaling molecule in biological systems, causes dispersal of P. aeruginosa biofilm bacteria. Dispersal was induced with low, sublethal concentrations (25 to 500 nM) of the NO donor sodium nitroprusside (SNP). Moreover, a P. aeruginosa mutant lacking the only enzyme capable of generating metabolic NO through anaerobic respiration (nitrite reductase, Δ nirS ) did not disperse, whereas a NO reductase mutant (Δ norCB ) exhibited greatly enhanced dispersal. Strategies to induce biofilm dispersal are of interest due to their potential to prevent biofilms and biofilm-related infections. We observed that exposure to SNP (500 nM) greatly enhanced the efficacy of antimicrobial compounds (tobramycin, hydrogen peroxide, and sodium dodecyl sulfate) in the removal of established P. aeruginosa biofilms from a glass surface. Combined exposure to both NO and antimicrobial agents may therefore offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.
Pseudomonas aeruginosa PAO1 Preferentially Grows as Aggregates in Liquid Batch Cultures and Disperses upon Starvation
Publisher: Public Library of Science (PLoS)
Date: 13-05-2009
Solvent optimization for bacterial extracellular matrices: a solution for the insoluble
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4RA10930A
Abstract: Ionic liquids enable solvent optimization for different biofilms through solubility parameter concept.
Nitric oxide and iron signaling cues have opposing effects on biofilm development in Pseudomonas aeruginosa
Publisher: American Society for Microbiology
Date: 02-2019
DOI: 10.1128/AEM.02175-18
Abstract: Nitric oxide (NO), which induces biofilm dispersal, is a promising strategy for biofilm control in both clinical and industrial contexts. However, competing environmental signals may reduce the efficacy of NO. The results presented here suggest that the presence of iron represents one such environmental cue that antagonizes the activity of NO as a biofilm-dispersing agent. Based on this understanding, we developed a strategy to enhance dispersal by combining NO with an iron-scavenging agent. Overall, this study links two important environmental signals, iron and NO, with their roles in biofilm development and suggests new ways for improving the use of NO in biofilm control strategies.
Erratum for “Dynamic Remodeling of Microbial Biofilms by Functionally Distinct Exopolysaccharides”
Publisher: American Society for Microbiology
Date: 07-2015
Dynamics of biofilm formation under different nutrient levels and the effect on biofouling of a reverse osmosis membrane system
Publisher: Informa UK Limited
Date: 03-2013
DOI: 10.1080/08927014.2013.772141
Abstract: Pseudomonas aeruginosa PAO1 wild type and a mucoid derivative (FRD1) which over produces alginate were used to foul reverse osmosis (RO) membranes. When operated at a constant flux, biofilm formation on the RO membrane resulted in a slow rise in transmembrane pressure (TMP) of 22% for the initial four days of operation, followed by a sharp increase of 159% over the following two days. The initial slow increase in TMP was probably due to the formation of a biofilm on the membrane surface, which then accelerated the rate of biofouling through the effect of concentration polarization. At later stages of operation, most of the bacterial biomass consisted of dead cells. The amount of extracellular polymeric substances appeared to correlate positively with the number of dead cells. The results indicate that prolonging the initial stage of slow TMP increase and avoiding the latter stage of accelerated TMP increase would provide a sustainable operation of the RO system. These results suggest that nutrient limitation could reduce biofilm accumulation and delay the increase in TMP.
Community quorum sensing signalling and quenching: Microbial granular biofilm assembly
Publisher: Springer Science and Business Media LLC
Date: 27-05-2015
DOI: 10.1038/NPJBIOFILMS.2015.6
Abstract: Recent reports exploring the role of gradients of quorum sensing (QS) signals in functional activated sludge have raised the question of whether shared systems of signalling synthesis and degradation, or quorum quenching (QQ), across the community inform of the means by which QS biology regulate floccular and granular biofilm assembly. In this study, we aimed to explore the species origin and interactive role of QS and QQ activities in such highly erse microbial biofilm communities. Here, such aims were addressed systematically by a comprehensive multi-pronged RNA-sequencing, microbiological and analytical chemistry experimental approach, using two related but independently evolved floccular and granular sludge communities. Our data revealed a distinct difference between the QS and QQ potentials of the two communities, with different species largely displaying either QS or QQ functions. The floccular sludge community showed a high rate of QQ activity, and this rate was dependent on the acyl chain length demonstrating specificity of degradation. When the floccular biomass was transformed into the granular sludge, the QQ activity of the community was reduced by 30%. N -acyl homoserine lactones with four to eight carbons on the acyl chain accumulated at the granular stage, and their concentrations were at least threefold higher than those of the floccular stage. These findings corroborated meta-community analysis where a major shift in the dominant species from potential signal quenchers to producers was observed during the transition from flocs to granules, indicating the role of species composition and associated signalling activities in coordinating community behaviours. This study suggests that QQ has an important function in regulating community level QS signalling, and provides a mechanistic insight into the role of QS biology in complex community assembly.
Effect of microbial community structure on organic removal and biofouling in membrane adsorption bioreactor used in seawater pretreatment
Publisher: Elsevier BV
Date: 06-2016
Mannitol Enhances Antibiotic Sensitivity of Persister Bacteria in Pseudomonas aeruginosa Biofilms
Publisher: Public Library of Science (PLoS)
Date: 13-12-2013
Design, synthesis and evaluation of N-aryl-glyoxamide derivatives as structurally novel bacterial quorum sensing inhibitors
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5OB01973G
Abstract: Bacteria cooperatively regulate the expression of many phenotypes through a mechanism called quorum sensing (QS).
The slippery business of slime control
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/MA07118
Abstract: What do that scummy feeling on your teeth in the morning, corrosion of oil and gas pipelines, and the slick film building up on the mystery food in the back of your refrigerator have in common? They are all manifestations of microbial slime, which is the result of bacteria growing as a community on a surface held together in an extracellular matrix. These are more commonly referred to as biofilms, which we constantly encounter in everyday life. Bacteria seem to favour growing as biofilms because this provides a range of distinct advantages, including better access to nutrients that partition to surfaces, protection from external stresses such as UV and inhibitors produced by competing microorganisms, and resistance to protozoan grazing that is otherwise one of the main mortality factors for bacteria.
N-Acyl Homoserine Lactone-Mediated Quorum Sensing Regulates Species Interactions in Multispecies Biofilm Communities
Publisher: Frontiers Media SA
Date: 18-03-2021
DOI: 10.3389/FCIMB.2021.646991
Abstract: Bacterial biofilms are important medically, environmentally and industrially and there is a need to understand the processes that govern functional synergy and dynamics of species within biofilm communities. Here, we have used a model, mixed-species biofilm community comprised of Pseudomonas aeruginosa PAO1, Pseudomonas protegens Pf-5 and Klebsiella pneumoniae KP1. This biofilm community displays higher biomass and increased resilience to antimicrobial stress conditions such as sodium dodecyl sulfate and tobramycin, compared to monospecies biofilm populations. P. aeruginosa is present at low proportions in the community and yet, it plays a critical role in community function, suggesting it acts as a keystone species in this community. To determine the factors that regulate community composition, we focused on P. aeruginosa because of its pronounced impact on community structure and function. Specifically, we evaluated the role of the N-acyl homoserine lactone (AHL) dependent quorum sensing (QS) system of P. aeruginosa PAO1, which regulates group behaviors including biofilm formation and the production of effector molecules. We found that mixed species biofilms containing P. aeruginosa QS mutants had significantly altered proportions of K. pneumoniae and P. protegens populations compared to mixed species biofilms with the wild type P. aeruginosa . Similarly, inactivation of QS effector genes, e.g. rhlA and pvdR , also governed the relative species proportions. While the absence of QS did not alter the proportions of the two species in dual species biofilms of P. aeruginosa and K. pneumoniae , it resulted in significantly lower proportions of P. aeruginosa in dual species biofilms with P. protegens . These observations suggest that QS plays an important role in modulating community biofilm structure and physiology and affects interspecific interactions.
Light Sheet Spectroscopy for the Investigation of Biofilms
Publisher: Elsevier BV
Date: 02-2018
Section 8 update: Detection of bacterial homoserine lactone quorum sensing signals
Publisher: Springer Netherlands
Date: 2008
Single microcolony diffusion analysis in Pseudomonas aeruginosa biofilms
Publisher: Springer Science and Business Media LLC
Date: 08-11-2019
DOI: 10.1038/S41522-019-0107-4
Abstract: The influence of the biofilm matrix on molecular diffusion is commonly hypothesized to be responsible for emergent characteristics of biofilms such as nutrient trapping, signal accumulation and antibiotic tolerance. Hence quantifying the molecular diffusion coefficient is important to determine whether there is an influence of biofilm microenvironment on the mobility of molecules. Here, we use single plane illumination microscopy fluorescence correlation spectroscopy (SPIM-FCS) to obtain 3D diffusion coefficient maps with micrometre spatial and millisecond temporal resolution of entire Pseudomonas aeruginosa microcolonies. We probed how molecular properties such as size and charge as well as biofilm properties such as microcolony size and depth influence diffusion of fluorescently labelled dextrans inside biofilms. The 2 MDa dextran showed uneven penetration and a reduction in diffusion coefficient suggesting that the biofilm acts as a molecular sieve. Its diffusion coefficient was negatively correlated with the size of the microcolony. Positively charged dextran molecules and positively charged antibiotic tobramycin preferentially partitioned into the biofilm and remained mobile inside the microcolony, albeit with a reduced diffusion coefficient. Lastly, we measured changes of diffusion upon induction of dispersal and detected an increase in diffusion coefficient inside the biofilm before any loss of biomass. Thus, the change in diffusion is a proxy to detect early stages of dispersal. Our work shows that 3D diffusion maps are very sensitive to physiological changes in biofilms, viz. dispersal. However, this study also shows that diffusion, as mediated by the biofilm matrix, does not account for the high level of antibiotic tolerance associated with biofilms.
Bacterial Communication Systems
Publisher: Wiley
Date: 07-03-2014
Laboratory and Field Testing Assessment of Next Generation Biocide-Free, Fouling-Resistant Slippery Coatings
Publisher: American Chemical Society (ACS)
Date: 06-10-2020
Sounding out bacteria: Microstructural effects of therapeutic ultrasound on bacterial biofilms
Publisher: Acoustical Society of America (ASA)
Date: 03-2019
DOI: 10.1121/1.5101864
Abstract: Treatment of chronic infections due to formation of bacterial biofilms are a huge risk due to the growing concerns with antimicrobial resistance. Biofilms grow in a complex and dynamic environment that weaken the effect of antimicrobials. Yet, the current strategy to tackle the problem is the development of novel drugs. However, the increasing prevalence of antimicrobial resistance suggests that an alternative treatment strategy without, or in synergy with, antibiotics is necessary to combat the biofilm infections. We and others have proposed high intensity focused ultrasound (HIFU) as a means to disrupt the biofilm matrix and improve therapy. Yet to date, there is limited knowledge on the cellular activity triggered by the biofilm-acoustic interactions. Here, we report the effect of HIFU at 500 kHz center frequency in absence of antibiotics or microbubbles on the microstructure of biofilms formed by Pseudomonas aeruginosa. Changes to the biofilm after acoustic exposure were characterized by confocal microscopy and electrochemical impedance spectroscopy. We observed a drop in the biomass at pressures where non-linear acoustics were dominant, and an increase in cellular activity. Our results suggest that there are acoustic bio-effects present in these bacteria that have not yet been reported.
Repetitive sequences found in the chromosome of the myxobacterium Nannocystis exedens are similar to msDNA: a possible retrotransposition event in bacteria.
Publisher: Wiley
Date: 02-1997
DOI: 10.1046/J.1365-2958.1997.2671627.X
Abstract: The first reverse transcriptase (RT) to be found in a prokaryotic cell is encoded by an element called a retron which resides in the chromosome of many different bacteria. In addition, all retrons code for a functionally obscure RNA-DNA satellite molecule called msDNA. msDNA is synthesized from an RNA template by the retron-encoded RT. An unusual retron element is described here from the myxobacterium Nannocystis exedens. This retron does not appear to have a typical RT gene in close proximity (1 kb) to the gene msd (which encodes the DNA strand of msDNA). The gene msr (which encodes the RNA strand of msDNA) appears to be duplicated and flanks both sides of the msd gene. Also discovered throughout the chromosome of this bacterium is a set of repeated sequences related to msDNA. These repeat sequences match only part of the sequences of msDNA and may have become incorporated into the chromosome of this bacterium by reverse transcription.
Elevated c-di-GMP Levels and Expression of the Type III Secretion System Promote Corneal Infection by Pseudomonas aeruginosa
Publisher: American Society for Microbiology
Date: 18-08-2022
DOI: 10.1128/IAI.00061-22
Abstract: Pseudomonas aeruginosa is generally believed to establish biofilm-associated infections under the regulation of the secondary messenger c-di-GMP. To evaluate P. aeruginosa biofilm physiology during ocular infections, comparative transcriptomic analysis was performed on wild-type P. aeruginosa PAO1, a Δ wspF mutant strain (high c-di-GMP levels), and a p lac - yhjH -containing strain (low c-di-GMP levels) from mouse corneal infection, as well as in vitro biofilm and planktonic cultures. The c-di-GMP content in P. aeruginosa during corneal infection was monitored using a fluorescent c-di-GMP reporter strain. Biofilm-related genes were induced in in vivo PAO1 compared to in vitro planktonic bacteria. Several diguanylate cyclases and phosphodiesterases were commonly regulated in in vivo PAO1 and in vitro biofilm compared to in vitro planktonic bacteria.
Cinnamaldehyde disrupts biofilm formation and swarming motility of pseudomonas aeruginosa
Publisher: Microbiology Society
Date: 09-2018
DOI: 10.1099/MIC.0.000692
Abstract: Bacterial biofilms can cause serious health care complications associated with increased morbidity and mortality. There is an urge to discover and develop new biofilm inhibitors from natural products or by modifying natural compounds or understanding the modes of action of existing compounds. Cinnamaldehyde (CAD), one of the major components of cinnamon oil, has been demonstrated to act as an antimicrobial agent against a number of Gram-negative and Gram-positive pathogens, including Pseudomonas aeruginosa, Helicobacter pylori and Listeria monocytogenes. Despite the mechanism of action of CAD against the model organism P. aeruginosa being undefined, based on its antimicrobial properties, we hypothesized that it may disrupt preformed biofilms of P. aeruginosa. The minimum inhibitory concentration (MIC) of CAD for planktonic P. aeruginosa was determined to be 11.8 mM. Membrane depolarization assays demonstrated disruption of the transmembrane potential of P. aeruginosa. CAD at 5.9 mM (0.5 MIC) disrupted preformed biofilms by 75.6 % and 3 mM CAD (0.25 MIC) reduced the intracellular concentrations of the secondary messenger, bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), which controls P. aeruginosa biofilm formation. The swarming motility of P. aeruginosa was also reduced by CAD in a concentration-dependent manner. Collectively, these findings show that sub-MICs of CAD can disrupt biofilms and other surface colonization phenotypes through the modulation of intracellular signalling processes.
Membrane adaptation limitations inEnterococcus faecalisunderlie sensitivity and the inability to develop significant resistance to conjugated oligoelectrolytes
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7RA11823F
Abstract: COEs are emerging antimicrobials to combat drug resistant infections and to which bacteria develop only limited resistance.
Machine Learning-Aided At-Line Detection of Bacterial marker NA for Cell Manufacturing
Publisher: Optica Publishing Group
Date: 2021
DOI: 10.1364/FIO.2021.JTU1A.93
Abstract: We show a machine learning-aided UV spectroscopy-based method using aseptic instrumentation to detect metabolite NA, a marker of microbial contamination. This potentially enables rapid, at-line microbial contamination detection in cell manufacturing.
Inhibition of luminescence and virulence in the black tiger prawn (Penaeus monodon) pathogen Vibrio harveyi by intercellular signal antagonists.
Publisher: American Society for Microbiology
Date: 05-2000
DOI: 10.1128/AEM.66.5.2079-2084.2000
Abstract: Expression of luminescence in the Penaeus monodon pathogen Vibrio harveyi is regulated by an intercellular quorum sensing mechanism involving the synthesis and detection of two signaling molecules, one of which is N -hydroxy butanoyl- l -homoserine lactone and the other of which is uncharacterized. Indirect evidence has suggested that virulence, associated with a toxic extracellular protein, and luminescence in V. harveyi are coregulated. In this study the effects of an acylated homoserine lactone antagonist produced by the marine alga Delisea pulchra on luminescence and toxin production in a virulent strain of V. harveyi were analyzed. Luminescence and toxin production were both inhibited by the signal antagonist at concentrations that had no impact on growth. Toxin production was found to be prematurely induced in V. harveyi cultures incubated in a 10% conditioned medium. Additionally, a significant reduction in the toxicity of concentrated supernatant extracts from V. harveyi cultures incubated in the presence of the signal antagonist, as measured by in vivo toxicity assays in mice and prawns, was observed. These results suggest that intercellular signaling antagonists have potential utility in the control of V. harveyi prawn infections.
Quantitative imaging and spectroscopic technologies for microbiology
Publisher: Oxford University Press (OUP)
Date: 24-03-2018
Abstract: Light microscopy has enabled the observation of the structure and organisation of biofilms. Typically, the contrast in an image obtained from light microscopy is given by the time-averaged intensity that is effective in visualising the overall structure. Technological advancements in light microscopy have led to the creation of techniques that not only provide a static intensity image of the biofilm, but also enable one to quantify various dynamic physicochemical properties of biomolecules in microbial biofilms. Such light microscopy-based techniques can be grouped into two main classes, those that are based on luminescence and those that are based on scattering. Here, we review the fundamentals and applications of luminescence and scattering-based techniques, specifically, fluorescence lifetime imaging, Förster resonance energy transfer, fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single-particle tracking, transient state imaging, and Brillouin and Raman microscopy. These techniques provide information about the abundance, interactions and mobility of various molecules in the biofilms and also properties of the local microenvironment at optical resolution. Further, one could use any of these techniques to probe the real-time changes in these physical parameters upon the addition of external agents or at different stages during the growth of biofilms.
Synthesis of cephalosporin-3′-diazeniumdiolates: Biofilm dispersing NO-donor prodrugs activated by β-lactamase
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC40869H
Abstract: Use of biofilm dispersing NO-donor compounds in combination with antibiotics has emerged as a promising new strategy for treating drug-resistant bacterial biofilm infections. This paper details the synthesis and preliminary evaluation of six cephalosporin-3'-diazeniumdiolates as biofilm-targeted NO-donor prodrugs. Each of the compounds is shown to selectively release NO following reaction with the bacteria-specific enzyme β-lactamase and to trigger dispersion of Pseudomonas aeruginosa biofilms in vitro.
Dose–response algorithms for water-bornePseudomonas aeruginosafolliculitis
Publisher: Cambridge University Press (CUP)
Date: 02-10-2014
DOI: 10.1017/S0950268814002532
Abstract: We developed two dose–response algorithms for P. aeruginosa pool folliculitis using bacterial and lesion density estimates, associated with undetectable, significant, and almost certain folliculitis. Literature data were fitted to Furumoto & Mickey's equations, developed for plant epidermis-invading pathogens: N l = A ln(1 + BC ) (log-linear model) P inf = 1−e (− r c C ) (exponential model), where A and B are 2.51644 × 10 7 lesions/m 2 and 2.28011 × 10 −11 c.f.u./ml P. aeruginosa , respectively C = pathogen density (c.f.u./ml), N l = folliculitis lesions/m 2 , P inf = probability of infection, and r C = 4·3 × 10 −7 c.f.u./ml P. aeruginosa . Outbreak data indicates these algorithms apply to exposure durations of 41 ± 25 min. Typical water quality benchmarks (≈10 −2 c.f.u./ml) appear conservative but still useful as the literature indicated repeated detection likely implies unstable control barriers and bacterial bloom potential. In future, culture-based outbreak testing should be supplemented with quantitative polymerase chain reaction and organic carbon assays, and quantification of folliculitis aetiology to better understand P. aeruginosa risks.
Green biolubricant infused slippery surfaces to combat marine biofouling
Publisher: Elsevier BV
Date: 05-2020
SmcR-Dependent Regulation of Adaptive Phenotypes in Vibrio vulnificus
Publisher: American Society for Microbiology
Date: 15-01-2001
DOI: 10.1128/JB.183.2.758-762.2001
Abstract: Vibrio vulnificus contains homologues of the V. harveyi luxR and luxS genes. A null mutation in smcR ( luxR ) resulted in a defect in starvation survival, inhibition of starvation-induced maintenance of culturability that occurs when V. vulnificus is starved prior to low-temperature incubation, and increased expression of stationary-phase phenotypes.
Pseudomonas aeruginosa PAO1 exopolysaccharides are important for mixed species biofilm community development and stress tolerance.
Publisher: Frontiers Media SA
Date: 20-08-2015
The role of quorum sensing signalling in EPS production and the assembly of a sludge community into aerobic granules
Publisher: Springer Science and Business Media LLC
Date: 16-01-2014
Minimal increase in genetic diversity enhances predation resistance
Publisher: Wiley
Date: 29-12-2011
The alternative sigma factor RpoN regulates the quorum sensing gene rhlI in Pseudomonas aeruginosa.
Publisher: Oxford University Press (OUP)
Date: 03-2003
Co-delivery of nitric oxide and antibiotic using polymeric nanoparticles
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SC02769A
Abstract: The rise of hospital-acquired infections, also known as nosocomial infections, is a growing concern in intensive healthcare, causing the death of hundreds of thousands of patients and costing billions of dollars worldwide every year.
College men and the birth rate - A note on the present day undergraduate mores relating to family size
Publisher: Oxford University Press (OUP)
Date: 1926
The correlation between biofilm biopolymer composition and membrane fouling in submerged membrane bioreactors
Publisher: Informa UK Limited
Date: 21-10-2014
DOI: 10.1080/08927014.2014.971238
Abstract: Biofouling, the combined effect of microorganism and biopolymer accumulation, significantly reduces the process efficiency of membrane bioreactors (MBRs). Here, four biofilm components, alpha-polysaccharides, beta-polysaccharides, proteins and microorganisms, were quantified in MBRs. The biomass of each component was positively correlated with the transmembrane pressure increase in MBRs. Proteins were the most abundant biopolymer in biofilms and showed the fastest rate of increase. The spatial distribution and co-localization analysis of the biofouling components indicated at least 60% of the extracellular polysaccharide (EPS) components were associated with the microbial cells when the transmembrane pressure (TMP) entered the jump phase, suggesting that the EPS components were either secreted by the biofilm cells or that the deposition of these components facilitated biofilm formation. It is suggested that biofilm formation and the accumulation of EPS are intrinsically coupled, resulting in biofouling and loss of system performance. Therefore, strategies that control biofilm formation on membranes may result in a significant improvement of MBR performance.
Furoxan Nitric Oxide Donors Disperse Pseudomonas aeruginosa Biofilms, Accelerate Growth, and Repress Pyoverdine Production
Publisher: American Chemical Society (ACS)
Date: 29-06-2017
DOI: 10.1021/ACSCHEMBIO.7B00256
Abstract: The use of nitric oxide (NO) as a signal for biofilm dispersal has been shown to increase the susceptibility of many biofilms to antibiotics, promoting their eradication. The delivery of NO to biofilms can be achieved by using NO donors with different kinetics and properties of NO release that can influence their efficacy as biofilm control agents. In this study, the kinetics of three furoxan derivatives were evaluated. The effects of these NO donors, which have an advantageous pharmacological profile of slower onset with an extended duration of action, on Pseudomonas aeruginosa growth, biofilm development, and dispersal were also characterized. Compound LL4254, which showed a fast rate of NO release, induced biofilm dispersal at approximately 200 μM. While LL4212 and LL4216 have a slower rate of NO release, both compounds could induce biofilm dispersal, under the same treatment conditions, when used at higher concentrations. In addition, LL4212 and LL4216 were found to promote P. aeruginosa growth in iron-limited minimal medium, leading to a faster rate of biofilm formation and glucose utilization, and ultimately resulted in early dispersal of biofilm cells through carbon starvation. High concentrations of LL4216 also repressed production of the siderophore pyoverdine by more than 50-fold, via both NO
Antibacterial Activity of Nanoparticles
Publisher: MDPI AG
Date: 25-05-2021
DOI: 10.3390/NANO11061391
Abstract: Antimicrobial resistance (AMR) is predicted to soon become one of the most serious threats to human and animal health [...]
Widespread and Indiscriminate Nanosilver Use: Genuine Potential for Microbial Resistance
Publisher: American Chemical Society (ACS)
Date: 24-03-2017
Abstract: In this era of increasing antibiotic resistance, the use of alternative antimicrobials such as silver has become more widespread. Superior antimicrobial activity has been provided through fabrication of silver nanoparticles or nanosilver (NAg), which imparts cytotoxic actions distinct from those of bulk silver. In the wake of the recent discoveries of bacterial resistance to NAg and its rising incorporation in medical and consumer goods such as wound dressings and dietary supplements, we argue that there is an urgent need to monitor the prevalence and spread of NAg microbial resistance. In this Perspective, we describe how the use of NAg in commercially available products facilitates prolonged microorganism exposure to bioavailable silver, which underpins the development of resistance. Furthermore, we advocate for a judicial approach toward NAg use in order to preserve its efficacy and to avoid environmental disruption.
Should we stay or should we go: mechanisms and ecological consequences for biofilm dispersal
Publisher: Springer Science and Business Media LLC
Date: 28-11-2011
DOI: 10.1038/NRMICRO2695
Abstract: In most environments, bacteria reside primarily in biofilms, which are social consortia of cells that are embedded in an extracellular matrix and undergo developmental programmes resulting in a predictable biofilm 'life cycle'. Recent research on many different bacterial species has now shown that the final stage in this life cycle includes the production and release of differentiated dispersal cells. The formation of these cells and their eventual dispersal is initiated through erse and remarkably sophisticated mechanisms, suggesting that there are strong evolutionary pressures for dispersal from an otherwise largely sessile biofilm. The evolutionary aspect of biofilm dispersal is now being explored through the integration of molecular microbiology with eukaryotic ecological and evolutionary theory, which provides a broad conceptual framework for the ersity of specific mechanisms underlying biofilm dispersal. Here, we review recent progress in this emerging field and suggest that the merging of detailed molecular mechanisms with ecological theory will significantly advance our understanding of biofilm biology and ecology.
Quorum sensing-regulated chitin metabolism provides grazing resistance to Vibrio cholerae biofilms
Publisher: Springer Science and Business Media LLC
Date: 23-01-2015
Succession of biofilm communities responsible for biofouling of membrane bio-reactors (MBRs).
Publisher: Public Library of Science (PLoS)
Date: 07-07-2017
Inhibition of the Quorum Sensing System, Elastase Production and Biofilm Formation in Pseudomonas aeruginosa by Psammaplin A and Bisaprasin
Publisher: MDPI AG
Date: 06-03-2022
DOI: 10.3390/MOLECULES27051721
Abstract: Natural products derived from marine sponges have exhibited bioactivity and, in some cases, serve as potent quorum sensing inhibitory agents that prevent biofilm formation and attenuate virulence factor expression by pathogenic microorganisms. In this study, the inhibitory activity of the psammaplin-type compounds, psammaplin A (1) and bisaprasin (2), isolated from the marine sponge, Aplysinellarhax, are evaluated in quorum sensing inhibitory assays based on the Pseudomonas aeruginosa PAO1 lasB-gfp(ASV) and rhlA-gfp(ASV) biosensor strains. The results indicate that psammaplin A (1) showed moderate inhibition on lasB-gfp expression, but significantly inhibited the QS-gene promoter, rhlA-gfp, with IC50 values at 14.02 μM and 4.99 μM, respectively. In contrast, bisaprasin (2) displayed significant florescence inhibition in both biosensors, PAO1 lasB-gfp and rhlA-gfp, with IC50 values at 3.53 μM and 2.41 μM, respectively. Preliminary analysis suggested the importance of the bromotyrosine and oxime functionalities for QSI activity in these molecules. In addition, psammaplin A and bisaprasin downregulated elastase expression as determined by the standard enzymatic elastase assay, although greater reduction in elastase production was observed with 1 at 50 μM and 100 μM. Furthermore, the study revealed that bisaprasin (2) reduced biofilm formation in P. aeruginosa.
Dispersal from microbial biofilms
Publisher: ASM Press
Date: 10-09-2015
Pseudomonas aeruginosa: A Model for Biofilm Formation
Publisher: Wiley
Date: 26-03-2008
Changes to the resistome of Pseudomonas aeruginosa clone ST308 associated with corneal infection over time
Publisher: Cold Spring Harbor Laboratory
Date: 11-04-2020
DOI: 10.1101/2020.04.10.036673
Abstract: This study compared the resistomes of isolates of Pseudomonas aeruginosa clone ST308 from 2018 and 1997 from India. Two ocular clonal type ST308 isolates of Pseudomonas aeruginosa (198 and 219) isolated in 2018 and five historical isolates (31, 32, 33, 35 and 37) isolated in 1997 at the LV Prasad Eye Institute in India were analysed for their susceptibilities to ciprofloxacin, levofloxacin, gentamicin, tobramycin, piperacillin, imipenem, ceftazidime and polymyxin B. DNA was extracted using the DNeasy® Blood and Tissue. Paired-end library was prepared using Nextera XT DNA library preparation kit. Libraries were sequenced on Illumina® MiSeq bench top sequencer generating 300 bp paired-end reads. Spades v3.12.0 was used for assembly, Resfinder v3.1. for acquired resistance genes and Snippy V2 for variants calling. Integron finder v1.5.1 was used to identify the integrons present in the genomes. The recent isolate 219 was resistant to all tested antibiotics except polymyxin while isolate 198 was resistant to ciprofloxacin, levofloxacin, gentamicin and tobramycin. Among historical isolates five were resistant to gentamicin, tobramycin and ciprofloxacin, four were resistant to levofloxacin while two were resistant to polymyxin. Twenty-four acquired resistance genes were present in the 2018 isolates compared to 11 in the historical isolates. All isolates contained the following genes encoding for aminoglycoside aph(6)-Id , aph(3′)-lIb, aph(3″)-Ib) , beta-lactam ( blaPAO) , tetracycline ( tet(G)) , fosfomycin (fosA) , chlor henicol ( catB7) , sulphonamide ( sul1) , quaternary ammonium ( qacEdelta1) and fluoroquinolone ( crpP) resistance. Isolate 198 possessed aph(3′)-VI , rmtD2, qnrVC1, blaOXA-488, blaPME-1 , while 219 possessed aadA1, rmtB, aac(6′)-Ib-cr, blaTEM-1B, blaVIM-2, mph(E), mph(A), msr(E) . In the isolate 219 genes blaTEM-1b , blaVIM-2 , sul1 , qnrvc1 , rmtB and aadA1 were carried on class 1 integron. While an incomplete class 1 integron was also found in isolate 198 which was located on the genome where gene rmtB , blaPME-1 , qnrVC1 and sul1 genes were positioned. There were no notable differences in the number of single nucleotide polymorphisms, but recent isolates carried more insertions and deletions in their genes. P. aeruginosa ocular clonal isolates have changed over time, with strains acquiring genes and having more insertions and deletions in their chromosomal genes that confirm resistance to antibiotics. Recent clonal ocular isolates of Pseudomonas aeruginosa from India have acquired a number of resistance genes compared to historical clones Consequently, resistance to antibiotics particularly fluoroquinolones in recent clones of P. aeruginosa appears to have increased. The acquired resistance genes found in the recent P. aeruginosa isolates were related to mobile genetic elements.
Bacterial quorum sensing and interference by naturally occurring biomimics
Publisher: Springer Science and Business Media LLC
Date: 26-09-2006
DOI: 10.1007/S00216-006-0761-2
Abstract: Bacteria are able to coordinate gene expression as a community through the secretion and detection of signalling molecules so that the members of the community can simultaneously express specific behaviours. This mechanism of regulation of behaviour appears to be a key trait for adaptation to specific environments and has been shown to regulate a variety of important phenotypes, from virulence factor production to biofilm formation to symbiosis related behaviours such as bioluminescence. The ability to communicate and communally regulate gene expression is hypothesised to have evolved as a way for organisms to delay expression of phenotypes until numerical supremacy is reached. For ex le, in the case of infection, if an invading microorganism were to express virulence factors too early, the host may be able to mount a successful defence and repel the invaders. There is growing evidence that bacterial quorum sensing (QS) systems are involved in cross-kingdom signalling with eukaryotic organisms and that eukaryotes are capable of actively responding to bacteria in their environment by detecting and acting upon the presence of these signalling molecules. Likewise, eukaryotes produce compounds that can interfere with QS systems in bacteria by acting as agonists or antagonists. An exciting new field of study, biomimetics, takes inspiration from nature's models and attempts to design solutions to human problems, and biomimics of QS systems may be one such solution. This article presents the acylated homoserine lactone and autoinducer 2 QS systems in bacteria, the means of intercepting or interfering with bacterial QS systems evolved by eukaryotes, and the rational design of synthetic antagonists.
Identification of Five Structurally Unrelated Quorum-Sensing Inhibitors of Pseudomonas aeruginosa from a Natural-Derivative Database
Publisher: American Society for Microbiology
Date: 11-2013
DOI: 10.1128/AAC.00955-13
Abstract: Bacteria communicate by means of small signal molecules in a process termed quorum sensing (QS). QS enables bacteria to organize their activities at the population level, including the coordinated secretion of virulence factors. Certain small-molecule compounds, known as quorum-sensing inhibitors (QSIs), have been shown to effectively block QS and subsequently attenuate the virulence of Pseudomonas aeruginosa , as well as increasing its susceptibility to both antibiotics and the immune system. In this study, a structure-based virtual screening (SB-VS) approach was used for the discovery of novel QSI candidates. Three-dimensional structures of 3,040 natural compounds and their derivatives were obtained, after which molecular docking was performed using the QS receptor LasR as a target. Based on docking scores and molecular masses, 22 compounds were purchased to determine their efficacies as quorum-sensing inhibitors. Using a live reporter assay for quorum sensing, 5 compounds were found to be able to inhibit QS-regulated gene expression in P. aeruginosa in a dose-dependent manner. The most promising compound, G1, was evaluated by isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis, and it was found to significantly affect the abundance of 46 proteins (19 were upregulated 27 were downregulated) in P. aeruginosa PAO1. It specifically reduced the expression of several quorum-sensing-regulated virulence factors, such as protease IV, chitinase, and pyoverdine synthetases. G1 was also able to reduce extracellular DNA release and inhibited the secretion of the virulence factor, elastase, whose expression is regulated by LasR. These results demonstrate the utility of SB-VS for the discovery of target-specific QSIs.
Nucleotide sequence analysis of NPS-1 β-lactamase and a novel integron (In1427)-carrying transposon in an MDR Pseudomonas aeruginosa keratitis strain
Publisher: Oxford University Press (OUP)
Date: 13-03-2018
DOI: 10.1093/JAC/DKY073
Nitric oxide signaling in Pseudomonas aeruginosa biofilms mediates phosphodiesterase activity, decreased cyclic di-GMP levels, and enhanced dispersal.
Publisher: American Society for Microbiology
Date: 12-2009
DOI: 10.1128/JB.00975-09
Abstract: Bacteria in biofilms often undergo active dispersal events and revert to a free-swimming, planktonic state to complete the biofilm life cycle. The signaling molecule nitric oxide (NO) was previously found to trigger biofilm dispersal in the opportunistic pathogen Pseudomonas aeruginosa at low, nontoxic concentrations (N. Barraud, D. J. Hassett, S. H. Hwang, S. A. Rice, S. Kjelleberg, and J. S. Webb, J. Bacteriol. 188:7344-7353, 2006). NO was further shown to increase cell motility and susceptibility to antimicrobials. Recently, numerous studies revealed that increased degradation of the secondary messenger cyclic di-GMP (c-di-GMP) by specific phosphodiesterases (PDEs) triggers a planktonic mode of growth in eubacteria. In this study, the potential link between NO and c-di-GMP signaling was investigated by performing (i) PDE inhibitor studies, (ii) enzymatic assays to measure PDE activity, and (iii) direct quantification of intracellular c-di-GMP levels. The results suggest a role for c-di-GMP signaling in triggering the biofilm dispersal event induced by NO, as dispersal requires PDE activity and addition of NO stimulates PDE and induces the concomitant decrease in intracellular c-di-GMP levels in P. aeruginosa . Furthermore, gene expression studies indicated global responses to low, nontoxic levels of NO in P. aeruginosa biofilms, including upregulation of genes involved in motility and energy metabolism and downregulation of adhesins and virulence factors. Finally, site-directed mutagenesis of candidate genes and physiological characterization of the corresponding mutant strains uncovered that the chemotaxis transducer BdlA is involved in the biofilm dispersal response induced by NO.
Interactions between microbial community members.
Publisher: Wiley
Date: 24-08-2017
An electrodynamics-Langevin dynamics (ED-LD) approach to simulate metal nanoparticle interactions and motion.
Publisher: The Optical Society
Date: 06-11-2015
DOI: 10.1364/OE.23.029978
A comparative study on nitric oxide and hypochlorite as a membrane cleaning agent to minimise biofilm growth in a membrane bioreactor (MBR) process
Publisher: Elsevier BV
Date: 08-2019
Bacterial signaling and signal responses as key factors in water and wastewater treatment
Publisher: Elsevier BV
Date: 12-2021
Real Time, Spatial, and Temporal Mapping of the Distribution of c-di-GMP during Biofilm Development.
Publisher: Elsevier BV
Date: 2017
Ectopic colonization of oral bacteria in the intestine drives TH1 cell induction and inflammation
Publisher: American Association for the Advancement of Science (AAAS)
Date: 20-10-2017
Abstract: Some gut conditions, such as inflammatory bowel disease (IBD), ulcerative colitis, and Crohn's disease (CD), are associated with imbalances in the gut microbe community. The causes of these intractable diseases have been difficult to discern. Atarashi et al. took s les from the mouths of IBD and CD patients and inoculated the extracted bacteria into germ-free mice (see the Perspective by Cao). Some of the inoculated mice showed strong proliferation of T helper 1 cells associated with the establishment of oral Klebsiella species in the colon. Klebsiella can be resistant to multiple antibiotics and are able to replace normal colon microbes after antibiotic therapy. Now we know that they probably originate from the mouth and could potentially contribute to bowel disease. Science , this issue p. 359 see also p. 308
In-situ monitoring of biofouling on reverse osmosis membranes: Detection and mechanistic study using electrical impedance spectroscopy
Publisher: Elsevier BV
Date: 11-2016
Graphene Oxide Mimics Biological Signaling Cue to Rescue Starving Bacteria
Publisher: Wiley
Date: 08-04-2021
Abstract: There is extensive debate about how 2D nanomaterials such as graphene oxide (GO) affect bacteria. Various effects of GO are proposed, including bacterial growth inhibition or enhancement, killing, and no activity. Herein, we report that GO protects Staphylococcus aureus bacterial cells from death in starvation conditions with up to a 1000‐fold improvement in cell viability. Transcriptomic profiling reveals that bacterial cells in starvation conditions generally shut down metabolic activity, while only cells incubated with GO increase production of specific enzymes involved in the glyoxalase detoxification pathway along with repressed autolysis. The oxygen‐containing functional groups of GO resemble the molecular structure of methylglyoxal, which bacteria produce to adapt to nutrient imbalances and is detoxified by glyoxalase enzymes. The ability of GO to enable bacterial cell survival in starvation conditions and accompanying cellular responses support that bacterial cells perceive GO as a methylglyoxal‐mimicking nanomaterial cue to reshuffle cellular metabolism and defenses.
Microbially influenced corrosion—Any progress?
Publisher: Elsevier BV
Date: 07-2020
Biofilms on living surfaces
Publisher: Wiley
Date: 14-05-2007
The role of quorum sensing and the effect of environmental conditions on biofilm formation by strains of Vibrio vulnificus.
Publisher: Informa UK Limited
Date: 2006
DOI: 10.1080/08927010600691879
Abstract: It has been suggested that Vibrio vulnificus attaches to plankton and algae and is found in large numbers in the environment. Factors affecting attachment, biofilm formation and morphology of V. vulnificus have not been thoroughly investigated. This study evaluated the role of quorum sensing (QS) and environmental conditions on biofilm development of V. vulnificus. It was found that biofilm development by V. vulnificus was affected by nutrient and glucose concentration, but not by NaCl concentration or temperature under the conditions used here. Moreover, biofilm development of a QS mutant strain proceeded rapidly and sloughing occurred earlier than for the isogenic parent strain. There was a significant loss of viability for the QS mutant biofilm early in development. Hence, it is hypothesised that factors regulated by the QS system play a role in proper biofilm development and maintenance of V. vulnificus. Furthermore, it is shown that biofilm development varied among isolates.
Full-Genome Sequence of Thalassotalea euphylliae H1, Isolated from a Montipora capitata Coral Located in Hawai’i
Publisher: American Society for Microbiology
Date: 21-11-2018
DOI: 10.1128/MRA.01244-18
Abstract: The isolate of Thalassotalea euphylliae H1 was collected from the surface of a Montipora capitata coral. The genome was assembled using long reads from a Nanopore MinION sequencer for scaffolding and complemented with short-read MiSeq sequences.
Matrix Polysaccharides and SiaD Diguanylate Cyclase Alter Community Structure and Competitiveness of Pseudomonas aeruginosa during Dual-Species Biofilm Development with
Publisher: American Society for Microbiology
Date: 21-12-2018
Abstract: Bacteria in natural and engineered environments form biofilms that include many different species. Microorganisms rely on a number of different strategies to manage social interactions with other species and to access resources, build biofilm consortia, and optimize growth. For ex le, Pseudomonas aeruginosa and Staphylococcus aureus are biofilm-forming bacteria that coinfect the lungs of cystic fibrosis patients and diabetic and chronic wounds. P. aeruginosa is known to antagonize S. aureus growth. However, many of the factors responsible for mixed-species interactions and outcomes such as infections are poorly understood. Biofilm bacteria are encased in a self-produced extracellular matrix that facilitates interspecies behavior and biofilm development. In this study, we examined the poorly understood roles of the major matrix biopolymers and their regulators in mixed-species biofilm interactions and development.
Predation by Bdellovibrio bacteriovorus significantly reduces viability and alters the microbial community composition of activated sludge flocs and granules
Publisher: Oxford University Press (OUP)
Date: 21-02-2017
Abstract: We recently isolated and characterised a predatory Bdellovibrio bacteriovorus strain from activated sludge (Ulu Pandan Water Reclamation Plant, Singapore), and this strain, B. bacteriovorus UP, was able to prey upon a broad spectrum of bacterial isolates from the activated sludge when grown as planktonic cells or as biofilms. Here, we have tested the effect of Bdellovibrio predation on floccular and granular sludge to determine if the spatial organisation, loosely or tightly aggregated communities, was protective from predation. The effect of predation was assessed using a combination of biomass quantification, cellular activity measurement and microscopic image analysis to determine community viability. Additionally, changes in the microbial communities due to predation by B. bacteriovorus UP were analysed through total RNA sequencing. Predation led to a significant reduction in microbial activity and total biomass for both floccular and granular sludge communities. Predation was also associated with significant changes in the microbial community composition in both communities, with >90% of the community members reduced in relative abundance after 24 h. Of those community members, the dominant organisms, such as Proteobacteria and Bacteroidetes, were the most affected phylotypes. This suggests that predatory bacteria, which display indiscriminant feeding, could significantly shift the species composition and thus, may disturb the operational performance of wastewater treatment systems.
The role of regulators in the expression of quorum-sensing signals in Pseudomonas aeruginosa.
Publisher: S. Karger AG
Date: 2003
DOI: 10.1159/000076739
Abstract: Quorum-sensing systems provide i Pseudomonas aeruginosa /i with a sensitive regulatory mechanism that allows for the induction of several phenotypic genes in a cell density fashion. In this work, a mathematical model of the acylated homoserine lactones regulatory network system in i P. aeruginosa /i has been developed. It is the first integrated model to consider both quorum-sensing systems. The model has allowed us to disentangle the complex behavior exhibited by the system as the concentration of extracellular OdDHL is increased. At either low or high levels of extracellular OdDHL, the bacterium remains in an uninduced or induced state, respectively. At moderate levels, the behavior is characterized by several states. Here, the bacteria can switch suddenly from an uninduced to an induced phenotype in response to small changes in the concentration of extracellular OdDHL. Additionally, we have been able to address the roles of RsaL and Vfr as regulators of the quorum-sensing system. An important result from this analysis suggests that RsaL will increase the concentration of extracellular OdDHL required to induce the system, and it is a key regulator of the inhibition of the quorum-sensing system under low cell densities. Most importantly, our results suggest that Vfr has strong regulatory effects on the system as an increased affinity between the LasR/OdDHL complex, and the i las /i R promoter leads to significant qualitative changes in induction patterns. We also show experimental data that demonstrate that Vfr is required for signal production in the early phase of growth, but that in the latter stages of growth, the i vfr /i mutant is able to synthesize wild-type levels of signal.
Mixed community biofilms and microbially influenced corrosion
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/MA18046
Abstract: Metals are used in most marine infrastructures for energy extraction and production. Metal corrosion is a serious concern, due to the environmental, safety, and replacement costs associated with it. Microbially influenced corrosion (MIC) contributes to the overall corrosion process, through several chemical, electrochemical and biochemical mechanisms, particularly in the presence of microbial biofilms. In this short article, we discuss briefly recent advances in MIC research, comparing corrosion in single species and mixed species biofilms, and outline possible strategies for biofilm and corrosion control.
Characterization of the archaeal community fouling a membrane bioreactor
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.JES.2014.07.025
Abstract: Biofilm formation, one of the primary causes of biofouling, results in reduced membrane flux or increased transmembrane pressure and thus represents a major impediment to the wider implementation of membrane bioreactor (MBR) technologies for water purification. Most studies have focused on the role of bacteria in membrane fouling as they are the most dominant and best studied organisms present in the MBR. In contrast, there is limited information on the role of the archaeal community in biofilm formation in MBRs. This study investigated the composition of the archaeal community during the process of biofouling in an MBR. The archaeal community was observed to have lower richness and ersity in the biofilm than the sludge during the establishment of biofilms at low transmembrane pressure (TMP). Clustering of the communities based on the Bray-Curtis similarity matrix indicated that a subset of the sludge archaeal community formed the initial biofilms. The archaeal community in the biofilm was mainly composed of Thermoprotei, Thermoplasmata, Thermococci, Methanopyri, Methanomicrobia and Halobacteria. Among them, the Thermoprotei and Thermoplasmata were present at higher relative proportions in the biofilms than they were in the sludge. Additionally, the Thermoprotei, Thermoplasmata and Thermococci were the dominant organisms detected in the initial biofilms at low TMP, while as the TMP increased, the Methanopyri, Methanomicrobia, Aciduliprofundum and Halobacteria were present at higher abundances in the biofilms at high TMP.
CONCEPTION, GESTATION AND BIRTH OF IASI
Publisher: JSTOR
Date: 06-1967
DOI: 10.2307/2682038
Novel Phage Lysin Abp013 against Acinetobacter baumannii
Publisher: MDPI AG
Date: 28-01-2022
DOI: 10.3390/ANTIBIOTICS11020169
Abstract: As antimicrobial resistance (AMR) continues to pose an ever-growing global health threat, propelling us into a post-antibiotic era, novel alternative therapeutic agents are urgently required. Lysins are bacteriophage-encoded peptidoglycan hydrolases that display great potential as a novel class of antimicrobials for therapeutics. While lysins against Gram-positive bacteria are highly effective when applied exogenously, it is challenging for lysins to access and cleave the peptidoglycan of Gram-negative bacteria due to their outer membrane. In this study, we identify a novel phage lysin Abp013 against Acinetobacter baumannii. Abp013 exhibited significant lytic activity against multidrug-resistant strains of A. baumannii. Notably, we found that Abp013 was able to tolerate the presence of human serum by up to 10%. Using confocal microscopy and LIVE/DEAD staining, we show that Abp013 can access and kill the bacterial cells residing in the biofilm. These results highlight the intrinsic bacteriolytic property of Abp013, suggesting the promising use of Abp013 as a novel therapeutic agent.
Induction of resistance to S. aureus in an environmental marine biofilm grown in Sydney Harbor, NSW, Australia.
Publisher: Springer Science and Business Media LLC
Date: 20-12-2015
DOI: 10.1007/S11274-014-1787-9
Abstract: The study of environmental biofilms is complicated by the difficulty of working with them under lab conditions. Nonetheless, knowledge of cellular activity and interactions within environmental biofilms could lead to novel biomedical applications. To address this problem we previously proposed a new technique for inducing resistance to Staphylococcus aureus in an intact environmental biofilm. In the current follow-up study we applied the new technique in a biogeographically distinct environment using a different strain of S. aureus. The proposed technique for inducing resistance to S. aureus in an environmental biofilm involves growing the environmental biofilms over several days in media reflecting their natural habitat on agar that contains spent culture supernatant from S. aureus over-night culture. We found in this second study that it was possible to induce resistance to S. aureus in an environmental biofilm from a biogeographically distinct environment, though not in the same way as we had previously observed. Environmental consortia from Sydney Harbor, Australia display an ability to inhibit biofilm formation by S. aureus only in the case where the environmental biofilms were pretreated with UV radiation was there a difference in activity between environmental consortia grown on plain agar, and that grown on S. aureus agar. Application of the new technique in the current study also differs in that significant killing of cells within an established S. aureus biofilm by environmental consortia grown on S. aureus agar was possible.
Characterisation and in vitro activities of surface attached dihydropyrrol-2-ones against Gram-negative and Gram-positive bacteria
Publisher: Informa UK Limited
Date: 27-10-2010
DOI: 10.1080/08927014.2010.531463
Abstract: Bacterial infection of biomedical devices is still a major barrier to their use. This is compounded by increasing antibiotic resistance. Here, the specific covalent attachment of a series of dihydropyrrol-2-one (DHP), analogues of bacterial quorum sensing inhibitors, to surfaces via a Michael-type addition reaction is described. Differences in efficiency of attachment related to the substituent groups were found by X-ray photoelectron spectroscopy. The physical characteristics of the surfaces were further explored by atomic force microscopy and contact angle measurements. The ability of these coatings to prevent the formation of a biofilm by Pseudomonas aeruginosa and Staphylococcus aureus was examined using confocal laser scanning microscopy and image analysis. The DHP-treated surfaces showed significant reductions in bacterial adhesion without increased killing for both strains of bacteria (p < 0.001). 5-Methylene-1-(prop-2-enoyl)-4-phenyl-dihydropyrrol-2-one was identified as having broad spectrum activity and consequently represents an excellent candidate for the development of novel surfaces for the prevention of biomedical device infections.
The role of quorum sensing mediated developmental traits in the resistance of Serratia marcescens biofilms against protozoan grazing.
Publisher: Wiley
Date: 16-02-2006
DOI: 10.1111/J.1462-2920.2006.00993.X
Abstract: Resistance against protozoan grazers is a crucial factor that is important for the survival of many bacteria in their natural environment. However, the basis of resistance to protozoans and how resistance factors are regulated is poorly understood. In part, resistance may be due to biofilm formation, which is known to protect bacteria from environmental stress conditions. The ubiquitous organism Serratia marcescens uses quorum sensing (QS) control to regulate virulence factor expression and biofilm formation. We hypothesized that the QS system of S. marcescens also regulates mechanisms that protect biofilms against protozoan grazing. To investigate this hypothesis, we compared the interactions of wild-type and QS mutant strains of S. marcescens biofilms with two protozoans having different feeding types under batch and flow conditions. Under batch conditions, S. marcescens forms microcolony biofilms, and filamentous biofilms are formed under flow conditions. The microcolony-type biofilms were protected from grazing by the suspension feeder, flagellate Bodo saltans, but were not protected from the surface feeder, Acanthamoeba polyphaga. In contrast, the filamentous biofilm provided protection against A. polyphaga. The main findings presented in this study suggest that (i) the QS system is not involved in grazing resistance of S. marcescens microcolony-type biofilms (ii) QS in S. marcescens regulates antiprotozoan factor(s) that do not interfere with the grazing efficiency of the protozoans and (iii) QS-controlled, biofilm-specific differentiation of filaments and cell chains in biofilms of S. marcescens provides an efficient mechanism against protozoan grazing.
SOCIAL ACCOUNTING AND STATISTICS FOR GREAT SOCIETY
Publisher: JSTOR
Date: 06-1967
DOI: 10.2307/974152
Next-generation studies of microbial biofilm communities.
Publisher: Wiley
Date: 29-07-2016
Complete Genome Sequence of Thalassotalea euphylliae Strain H2
Publisher: American Society for Microbiology
Date: 24-01-2019
DOI: 10.1128/MRA.01608-18
Abstract: A bacterial isolate of Thalassotalea euphylliae H2 was collected from the coral Montipora capitata . MinION long reads were employed for scaffolding and complemented with short-read MiSeq sequences to permit complete genome assembly.
Acquired fluoroquinolone resistance genes in corneal isolates of Pseudomonas aeruginosa
Publisher: Elsevier BV
Date: 11-2020
Analysis of microbial community composition in a lab‐scale membrane distillation bioreactor
Publisher: Oxford University Press (OUP)
Date: 15-02-2015
DOI: 10.1111/JAM.12759
The presence and role of bacterial quorum sensing in activated sludge
Publisher: Wiley
Date: 14-05-2012
The Repressor C Protein, Pf4r, Controls Superinfection of Pseudomonas aeruginosa PAO1 by the Pf4 Filamentous Phage and Regulates Host Gene Expression
Publisher: MDPI AG
Date: 15-08-2021
DOI: 10.3390/V13081614
Abstract: It has been shown that the filamentous phage, Pf4, plays an important role in biofilm development, stress tolerance, genetic variant formation and virulence in Pseudomonas aeruginosa PAO1. These behaviours are linked to the appearance of superinfective phage variants. Here, we have investigated the molecular mechanism of superinfection as well as how the Pf4 phage can control host gene expression to modulate host behaviours. Pf4 exists as a prophage in PAO1 and encodes a homologue of the P2 phage repressor C and was recently named Pf4r. Through a combination of molecular techniques, ChIPseq and transcriptomic analyses, we show a critical site in repressor C (Pf4r) where a mutation in the site, 788799A G (Ser4Pro), causes Pf4r to lose its function as the immunity factor against reinfection by Pf4. X-ray crystal structure analysis shows that Pf4r forms symmetric homo-dimers homologous to the E.coli bacteriophage P2 RepC protein. A mutation, Pf4r*, associated with the superinfective Pf4r variant, found at the dimer interface, suggests dimer formation may be disrupted, which derepresses phage replication. This is supported by multi-angle light scattering (MALS) analysis, where the Pf4r* protein only forms monomers. The loss of dimerisation also explains the loss of Pf4r’s immunity function. Phenotypic assays showed that Pf4r increased LasB activity and was also associated with a slight increase in the percentage of morphotypic variants. ChIPseq and transcriptomic analyses suggest that Pf4r also likely functions as a transcriptional regulator for other host genes. Collectively, these data suggest the mechanism by which filamentous phages play such an important role in P. aeruginosa biofilm development.
Bacterial reverse transcriptase and msDNA.
Publisher: Springer Science and Business Media LLC
Date: 06-1995
DOI: 10.1007/BF01728651
Direct visualization of bacterial multispecies infection and symbiotic interactions within human bladder epithelial cells
Publisher: Cold Spring Harbor Laboratory
Date: 17-02-2023
DOI: 10.1101/2023.02.16.528894
Abstract: Urinary tract infections (UTIs) are a worsening global health problem. Multispecies bacterial UTIs are common but are poorly recognized and understood. Here we developed host cell co-infection models combined with high resolution imaging to compare single- and multi-species infections with common uropathogens, uropathogenic Escherichia coli (UPEC), Klebsiella pneumoniae and Enterococcus faecalis . We demonstrate cooperation and direct interactions specifically between UPEC and E. faecalis within host cells that corresponded to an increased frequency of host cell infection. 3D imaging showed UPEC rods orientated perpendicular to the major host cell axis within single-species intracellular bacterial communities (IBCs), whereas UPEC cells often enveloped E. faecalis in multispecies IBCs. Furthermore, during dispersal from host cells, only the Gram-negative bacteria underwent infection-related filamentation (IRF) in multispecies infections. These first insights into intra-species synergies during UTIs at a single cell level should provide research pathways towards better diagnosis and treatment.
Engineering a light-responsive, quorum quenching biofilm to mitigate biofouling on water purification membranes
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-12-2018
Abstract: We engineered a light-responsive, quorum quenching biofilm and demonstrated its application in mitigating membrane biofouling.
Dihydropyrrolones as bacterial quorum sensing inhibitors
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.BMCL.2019.03.004
Abstract: Bacteria regulate their pathogenicity and biofilm formation through quorum sensing (QS), which is an intercellular communication system mediated by the binding of signaling molecules to QS receptors such as LasR. In this study, a range of dihydropyrrolone (DHP) analogues were synthesized via the lactone-lactam conversion of lactone intermediates. The synthesized compounds were tested for their ability to inhibit QS, biofilm formation and bacterial growth of Pseudomonas aeruginosa. The compounds were also docked into a LasR crystal structure to rationalize the observed structure-activity relationships. The most active compound identified in this study was compound 9i, which showed 63.1% QS inhibition of at 31.25 µM and 60% biofilm reduction at 250 µM with only moderate toxicity towards bacterial cell growth.
Onset of Microbial Influenced Corrosion (MIC) in Stainless Steel Exposed to Mixed Species Biofilms from Equatorial Seawater
Publisher: The Electrochemical Society
Date: 2017
DOI: 10.1149/2.0521709JES
The application of nitric oxide to control biofouling of membrane bioreactors
Publisher: Wiley
Date: 06-03-2015
Quorum‐sensing cross talk: isolation and chemical characterization of cyclic dipeptides from Pseudomonas aeruginosa and other Gram‐negative bacteria
Publisher: Wiley
Date: 09-1999
DOI: 10.1046/J.1365-2958.1999.01577.X
Abstract: In cell-free Pseudomonas aeruginosa culture supernatants, we identified two compounds capable of activating an N-acylhomoserine lactone (AHL) biosensor. Mass spectrometry and NMR spectroscopy revealed that these compounds were not AHLs but the diketopiperazines (DKPs), cyclo(DeltaAla-L-Val) and cyclo(L-Pro-L-Tyr) respectively. These compounds were also found in cell-free supernatants from Proteus mirabilis, Citrobacter freundii and Enterobacter agglomerans [cyclo(DeltaAla-L-Val) only]. Although both DKPs were absent from Pseudomonas fluorescens and Pseudomonas alcaligenes, we isolated, from both pseudomonads, a third DKP, which was chemically characterized as cyclo(L-Phe-L-Pro). Dose-response curves using a LuxR-based AHL biosensor indicated that cyclo(DeltaAla-L-Val), cyclo(L-Pro-L-Tyr) and cyclo(L-Phe-L-Pro) activate the biosensor in a concentration-dependent manner, albeit at much higher concentrations than the natural activator N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). Competition studies showed that cyclo(DeltaAla-L-Val), cyclo(L-Pro-L-Tyr) and cyclo(L-Phe-L-Pro) antagonize the 3-oxo-C6-HSL-mediated induction of bioluminescence, suggesting that these DKPs may compete for the same LuxR-binding site. Similarly, DKPs were found to be capable of activating or antagonizing other LuxR-based quorum-sensing systems, such as the N-butanoylhomoserine lactone-dependent swarming motility of Serratia liquefaciens. Although the physiological role of these DKPs has yet to be established, their activity suggests the existence of cross talk among bacterial signalling systems.
The SiaABC threonine phosphorylation pathway controls biofilm formation in response to carbon availability in Pseudomonas aeruginosa
Publisher: Public Library of Science (PLoS)
Date: 06-11-2020
DOI: 10.1371/JOURNAL.PONE.0241019
Abstract: The critical role of bacterial biofilms in chronic human infections calls for novel anti-biofilm strategies targeting the regulation of biofilm development. However, the regulation of biofilm development is very complex and can include multiple, highly interconnected signal transduction/response pathways, which are incompletely understood. We demonstrated previously that in the opportunistic, human pathogen P . aeruginosa , the PP2C-like protein phosphatase SiaA and the di-guanylate cyclase SiaD control the formation of macroscopic cellular aggregates, a type of suspended biofilms, in response to surfactant stress. In this study, we demonstrate that the SiaABC proteins represent a signal response pathway that functions through a partner switch mechanism to control biofilm formation. We also demonstrate that SiaABCD functionality is dependent on carbon substrate availability for a variety of substrates, and that upon carbon starvation, SiaB mutants show impaired dispersal, in particular with the primary fermentation product ethanol. This suggests that carbon availability is at least one of the key environmental cues integrated by the SiaABCD system. Further, our biochemical, physiological and crystallographic data reveals that the phosphatase SiaA and its kinase counterpart SiaB balance the phosphorylation status of their target protein SiaC at threonine 68 (T68). Crystallographic analysis of the SiaA-PP2C domain shows that SiaA is present as a dimer. Dynamic modelling of SiaA with SiaC suggested that SiaA interacts strongly with phosphorylated SiaC and dissociates rapidly upon dephosphorylation of SiaC. Further, we show that the known phosphatase inhibitor fumonisin inhibits SiaA mediated phosphatase activity in vitro . In conclusion, the present work improves our understanding of how P . aeuruginosa integrates specific environmental conditions, such as carbon availability and surfactant stress, to regulate cellular aggregation and biofilm formation. With the biochemical and structural characterization of SiaA, initial data on the catalytic inhibition of SiaA, and the interaction between SiaA and SiaC, our study identifies promising targets for the development of biofilm-interference drugs to combat infections of this aggressive opportunistic pathogen.
Phenotypic and integrated analysis of a comprehensive Pseudomonas aeruginosa PAO1 library of mutants lacking cyclic-di-GMP-related genes
Publisher: Frontiers Media SA
Date: 22-07-2022
DOI: 10.3389/FMICB.2022.949597
Abstract: Pseudomonas aeruginosa is a Gram-negative bacterium that is able to survive and adapt in a multitude of niches as well as thrive within many different hosts. This versatility lies within its large genome of ca. 6 Mbp and a tight control in the expression of thousands of genes. Among the regulatory mechanisms widespread in bacteria, cyclic-di-GMP signaling is one which influences all levels of control. c-di-GMP is made by diguanylate cyclases and degraded by phosphodiesterases, while the intracellular level of this molecule drives phenotypic responses. Signaling involves the modification of enzymes’ or proteins’ function upon c-di-GMP binding, including modifying the activity of regulators which in turn will impact the transcriptome. In P. aeruginosa , there are ca. 40 genes encoding putative DGCs or PDEs. The combined activity of those enzymes should reflect the overall c-di-GMP concentration, while specific phenotypic outputs could be correlated to a given set of dgc de . This notion of specificity has been addressed in several studies and different strains of P. aeruginosa . Here, we engineered a mutant library for the 41 in idual dgc de genes in P. aeruginosa PAO1. In most cases, we observed a significant to slight variation in the global c-di-GMP pool of cells grown planktonically, while several mutants display a phenotypic impact on biofilm including initial attachment and maturation. If this observation of minor changes in c-di-GMP level correlating with significant phenotypic impact appears to be true, it further supports the idea of a local vs global c-di-GMP pool. In contrast, there was little to no effect on motility, which differs from previous studies. Our RNA-seq analysis indicated that all PAO1 dgc de genes were expressed in both planktonic and biofilm growth conditions and our work suggests that c-di-GMP networks need to be reconstructed for each strain separately and cannot be extrapolated from one to another.
Cephalosporin‐3′‐diazeniumdiolates: Targeted NO‐Donor Prodrugs for Dispersing Bacterial Biofilms
Publisher: Wiley
Date: 13-08-2012
Effects of Surface Composition on the Aerosolisation and Dissolution of Inhaled Antibiotic Combination Powders Consisting of Colistin and Rifampicin
Publisher: Springer Science and Business Media LLC
Date: 24-11-2015
Dynamic Remodeling of Microbial Biofilms by Functionally Distinct Exopolysaccharides
Publisher: American Society for Microbiology
Date: 29-08-2014
Abstract: Biofilms are densely populated communities of microbial cells protected and held together by a matrix of extracellular polymeric substances. The structure and rheological properties of the matrix at the microscale influence the retention and transport of molecules and cells in the biofilm, thereby dictating population and community behavior. Despite its importance, quantitative descriptions of the matrix microstructure and microrheology are limited. Here, particle-tracking microrheology in combination with genetic approaches was used to spatially and temporally study the rheological contributions of the major exopolysaccharides Pel and Psl in Pseudomonas aeruginosa biofilms. Psl increased the elasticity and effective cross-linking within the matrix, which strengthened its scaffold and appeared to facilitate the formation of microcolonies. Conversely, Pel reduced effective cross-linking within the matrix. Without Psl, the matrix becomes more viscous, which facilitates biofilm spreading. The wild-type biofilm decreased in effective cross-linking over time, which would be advantageous for the spreading and colonization of new surfaces. This suggests that there are regulatory mechanisms to control production of the exopolysaccharides that serve to remodel the matrix of developing biofilms. The exopolysaccharides were also found to have profound effects on the spatial organization and integration of P. aeruginosa in a mixed-species biofilm model of P. aeruginosa - Staphylococcus aureus . Pel was required for close association of the two species in mixed-species microcolonies. In contrast, Psl was important for P. aeruginosa to form single-species biofilms on top of S. aureus biofilms. Our results demonstrate that Pel and Psl have distinct physical properties and functional roles during biofilm formation. IMPORTANCE Most bacteria grow as biofilms in the environment or in association with eukaryotic hosts. Removal of biofilms that form on surfaces is a challenge in clinical and industrial settings. One of the defining features of a biofilm is its extracellular matrix. The matrix has a heterogeneous structure and is formed from a secretion of various biopolymers, including proteins, extracellular DNA, and polysaccharides. It is generally known to interact with biofilm cells, thus affecting cell physiology and cell-cell communication. Despite the fact that the matrix may comprise up to 90% of the biofilm dry weight, how the matrix properties affect biofilm structure, maturation, and interspecies interactions remain largely unexplored. This study reveals that bacteria can use specific extracellular polymers to modulate the physical properties of their microenvironment. This in turn impacts biofilm structure, differentiation, and interspecies interactions.
Voltammetric profiling of redox-active metabolites expressed by Pseudomonas aeruginosa for diagnostic purposes
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4CC08590F
Abstract: Voltammetric analysis of Pseudomonas aeruginosa growth cultures unveils the interplay between PQS and phenazines under a potential bias.
Glucose Starvation-Induced Dispersal of Pseudomonas aeruginosa Biofilms Is cAMP and Energy Dependent
Publisher: Public Library of Science (PLoS)
Date: 14-08-2012
Enhancing Bidirectional Electron Transfer of Shewanella oneidensis by a Synthetic Flavin Pathway
Publisher: American Chemical Society (ACS)
Date: 05-02-2015
DOI: 10.1021/SB500331X
Abstract: Flavins regulate the rate and direction of extracellular electron transfer (EET) in Shewanella oneidensis. However, low concentration of endogenously secreted flavins by the wild-type S. oneidensis MR-1 limits its EET efficiency in bioelectrochemical systems (BES). Herein, a synthetic flavin biosynthesis pathway from Bacillus subtilis was heterologously expressed in S. oneidensis MR-1, resulting in ∼25.7 times' increase in secreted flavin concentration. This synthetic flavin module enabled enhanced bidirectional EET rate of MR-1, in which its maximum power output in microbial fuel cells increased ∼13.2 times (from 16.4 to 233.0 mW/m(2)), and the inward current increased ∼15.5 times (from 15.5 to 255.3 μA/cm(2)).
A partial copy of msDNA from a new retron element is likely a retrotransposed DNA found in the myxobacterium Nannocystis exedens.
Publisher: Elsevier BV
Date: 10-2002
DOI: 10.1016/S0378-1119(02)00977-0
Abstract: Retrons are reverse transcriptase (RT) encoding genetic elements usually located on the chromosome of a wide variety of mostly Gram-negative bacteria. Here we describe a new retron, designated Ne144, found in the chromosome of the myxobacterium Nannocystis exedens. This element codes for a 515-amino-acid RT that is most closely related to those found in other myxobacterial retrons. The RT is responsible for the production of a small satellite DNA called msDNA. This msDNA is composed of a 144 base, single-stranded DNA that is linked to a 72 base single-stranded RNA. The RNA strand is joined to the 5' end of the DNA chain via a 2'-5' linkage that occurs from the 2' position of an internal guanosine residue in the RNA. In addition to the retron element, the chromosome of N. exedens also contains several partial copies of the msDNA sequence as revealed by DNA hybridization experiments using msDNA as a probe. One of these partial copies was characterized from a chromosome restriction fragment and found to contain a sequence that matches the last 82 bases of the DNA strand and five bases of the RNA strand in msDNA-Ne144. This partial copy of msDNA is very likely a retrotransposed sequence that was generated by reverse transcription using an RNA (the primer-template RNA for msDNA) as a template and the 3' end of a nick in the chromosome as a primer, followed by incorporation into an open reading frame. The presence of this truncated copy of msDNA is strong evidence of retrotransposition in N. exedens causing an alteration in the bacterial genome.
Pseudomonas aeruginosawithLasIQuorum-Sensing Deficiency during Corneal Infection
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-2004
DOI: 10.1167/IOVS.03-0980
Abstract: To understand the importance of Pseudomonas aeruginosa quorum-sensing systems in the development of corneal infection, the genotypic characteristics and pathogenesis of seven ocular isolates with low-protease and acyl homoserine lactone (AHL) activity and quorum-sensing mutants of PAO1 deficient in lasI, lasR, or rhlR were investigated in the study. The possession of the quorum-sensing genes lasI, lasR, rhlI, rhlR, and the quorum-sensing controlled genes lasB, aprA, and rhlAB in the clinical isolates were determined by polymerase chain reaction and Southern blot hybridization. Elastinolytic activity, controlled by the las system, was assayed using elastin Congo red and rhamnolipid production controlled by the rhl system was assessed using agar plates containing methylene blue/cetyltrimethyl ammonium bromide. Induction of keratitis was examined in a scarified inbred BALB/c mouse model. The clinical isolates Paer1 and -3 were lasI and lasR negative, and the isolates Paer2 and -4 were rhlR and rhlAB negative. The isolates Paer17, Paer26, 6294 and 6206 possessed all the genes examined. There was no rhamnolipid production in clinical isolates Paer2 and -4. The isolates Paer1 and -3 were virtually avirulent in the scarified mouse corneas. Using isogenic PAO1 mutants, strain lasI showed a markedly reduced virulence in the corneal infection model. The remainder of the clinical isolates and the lasR or rhlR mutant strains caused severe keratitis. These results indicate that quorum-sensing deficiency may occur naturally in clinical isolates, and the possession of lasI and hence a functional Las quorum-sensing system may be important in development of corneal infection.
TOWARD ONE WORLD IN STATISTICS - DIPS AND GAPS IN AN UPWARD TREND
Publisher: JSTOR
Date: 1968
DOI: 10.2307/1401466
Modification of in vivo and in vitro T- and B-cell-mediated immune responses by the Pseudomonas aeruginosa quorum-sensing molecule n-(3-oxododecanoyl)-L-homoserine lactone
Publisher: American Society for Microbiology
Date: 08-2003
DOI: 10.1128/IAI.71.8.4421-4431.2003
Abstract: N -3-(oxododecanoyl)- l -homoserine lactone (OdDHL), a quorum-sensing molecule of Pseudomonas aeruginosa , plays an important role in the pathogenesis of the organism through its control of virulence factor expression. Several reports have suggested that OdDHL can also directly modulate host immune responses. However, the nature of the modulation is controversial, with different reports suggesting promotion of either humoral (Th2-mediated) or inflammatory (Th1-mediated) responses. This report describes a series of studies which demonstrate for the first time that in vivo administration of OdDHL can modulate the course of an antibody response, with an increase in ovalbumin (OVA)-specific immunogloblulin G1 (IgG1) but not IgG2a in OdDHL-treated OVA-immunized BALB/c mice compared to levels for controls. In vitro stimulation of lymphocytes from both Th1-biased C57Bl/6 and T-cell receptor transgenic mice and Th2-biased BALB/c mice in the presence of OdDHL demonstrated that OdDHL inhibits in vitro cytokine production in response to both mitogen and antigen, with gamma interferon (IFN-γ) tending to be more inhibited than interleukin-4 (IL-4). In vitro mitogen or antigen restimulation of cells from mice treated with OdDHL in vivo shows effects on cytokine production which depend on the underlying immune bias of the mouse strain used, with a relative increase of IFN-γ in Th1-biased C57Bl/6 mice and a relative increase of IL-4 in Th2-biased BALB/c mice. Thus, the mode of action of OdDHL on T-cell cytokine production is likely to be a relatively nonspecific one which accentuates an underlying immune response bias rather than one which specifically targets either Th1 or Th2 responses.
Pseudomonas aeruginosaisolates co-incubated withAcanthamoeba castellaniiexhibit phenotypes similar to chronic cystic fibrosis isolates
Publisher: Cold Spring Harbor Laboratory
Date: 25-02-2020
DOI: 10.1101/2020.02.25.964320
Abstract: The opportunistic pathogen, Pseudomonas aeruginosa , is ubiquitous in the environment, and in humans is capable of causing acute and chronic infections. P. aeruginosa , when co-incubated with the bacterivorous amoeba, Acanthamoeba castellanii , for extended periods, produced genetic and phenotypic variants. Sequencing of late-stage amoeba-adapted P. aeruginosa isolates demonstrated single nucleotide polymorphisms within genes that encode known virulence factors, and this correlated with a reduction in expression of virulence traits. Virulence towards the nematode, Caenorhabditis elegans , was attenuated in late-stage amoeba-adapted P. aeruginosa compared to early stage amoeba-adapted and non-adapted counterparts. Late-stage amoeba-adapted P. aeruginosa lost competitive fitness compared to non-adapted counterparts when grown in nutrient rich media. However, non-adapted P. aeruginosa were rapidly cleared by amoeba predation, whereas late-stage amoeba-adapted isolates remained in higher numbers 24 h after ingestion by amoeba. In addition, there was reduced uptake by macrophage of amoeba-adapted isolates and reduced uptake by human neutrophils as well as increased survival in the presence of neutrophils. Our findings indicate that the selection imposed by amoeba on P. aeruginosa resulted in reduced virulence over time. Importantly, the genetic and phenotypic traits possessed by late-stage amoeba-adapted P. aeruginosa are similar to what is observed for isolates obtained from chronic cystic fibrosis infections. This notable overlap in adaptation to different host types suggests similar selection pressures among host cell types. Pseudomonas aeruginosa is an opportunistic pathogen that causes both acute infections in plants and animals, including humans and also causes chronic infections in immune compromised and cystic fibrosis patients. This bacterium is commonly found in soils and water where bacteria are constantly under threat of being consumed by the bacterial predators, protozoa. To escape being killed, bacteria have evolved a suite of mechanisms that protect them from being consumed or digested. Here we examined the effect of long-term predation on the genotype and phenotypes expressed by P. aeruginosa. We show that long-term co-incubation with protozoa resulted in mutations in the bacteria that made them less pathogenic. This is particularly interesting as we see similar mutations arise in bacteria associated with chronic infections. Thus, predation by protozoa and long term colonization of the human host may represent similar environments that select for similar losses in gene functions.
The effects of high intensity focused ultrasound on biofilms formed by Pseudomonas aeruginosa
Publisher: Acoustical Society of America (ASA)
Date: 03-2018
DOI: 10.1121/1.5036297
Abstract: Bacterial infections are increasingly difficult to treat due to their growing resistance to antibiotics. Most of these bacterial infections form a biofilm that limits the effectiveness of the antibiotic. Biofilms are microbial cells that are protected by a self-generated matrix of extracellular polymeric substances. In addition to their intrinsic antibiotic resistance, these biofilms are able to respond to the stresses from the antibiotic by inducing drug resistance mechanisms. Currently, the strategy to combat drug resistance is to develop novel drugs, however, the rate of drug development is being surpassed by the rate of drug resistance. There is therefore a need for alternative means in enhancing the efficacy of current drug therapeutics. We propose to use of high intensity focused ultrasound (HIFU) to disrupt the biofilm and promote drug penetration. However, the effects of HIFU on these bacterial communities remain unknown. Here we report on microstructural changes within biofilms formed by Pseudomonas aeruginosa due to exposure to HIFU at 500 kHz center frequency. Changes to the biofilm were nondestructively measured through impedance spectroscopy and confocal microscopy. Biofilms were shown to induce cavitation (as measured by a passive cavitation detector) at relatively low pressure litudes suggesting the presence of cavitation nuclei within the extracellular matrix.
Functional metagenomic analysis of quorum sensing signaling in a nitrifying community
Publisher: Springer Science and Business Media LLC
Date: 28-10-2021
DOI: 10.1038/S41522-021-00250-3
Abstract: Quorum sensing (QS) can function to shape the microbial community interactions, composition, and function. In wastewater treatment systems, acylated homoserine lactone (AHL)-based QS has been correlated with the conversion of floccular biomass into microbial granules, as well as EPS production and the nitrogen removal process. However, the role of QS in such complex communities is still not fully understood, including the QS-proficient taxa and the functional QS genes involved. To address these questions, we performed a metagenomic screen for AHL genes in an activated sludge microbial community from the Ulu Pandan wastewater treatment plant (WWTP) in Singapore followed by functional validation of luxI activity using AHL biosensors and LC–MSMS profiling. We identified 13 luxI and 30 luxR homologs from the activated sludge metagenome. Of those genes, two represented a cognate pair of luxIR genes belonging to a Nitrospira spp. and those genes were demonstrated to be functionally active. The LuxI homolog synthesized AHLs that were consistent with the dominant AHLs in the activated sludge system. Furthermore, the LuxR homolog was shown to bind to and induce expression of the luxI promoter, suggesting this represents an autoinduction feedback system, characteristic of QS circuits. Additionally, a second, active promoter was upstream of a gene encoding a protein with a GGDEF/EAL domain, commonly associated with modulating the intracellular concentration of the secondary messenger, c-di-GMP. Thus, the metagenomic approach used here was demonstrated to effectively identify functional QS genes and suggests that Nitrospira spp. maybe QS is active in the activated sludge community.
Increased iron utilization and oxidative stress tolerance in a Vibrio cholerae flrA mutant confers resistance to amoeba predation
Publisher: American Society for Microbiology
Date: 26-10-2023
DOI: 10.1128/AEM.01095-23
CO-Releasing Polymers Exert Antimicrobial Activity
Publisher: American Chemical Society (ACS)
Date: 05-08-2015
DOI: 10.1021/ACS.BIOMAC.5B00716
Abstract: Infectious diseases remain one of the leading causes of death worldwide despite the tremendous effort devoted to the design and development of antimicrobial agents. However, the decrease in the effectiveness of some antibiotics is often associated with the development of drug resistance by pathogen. This leads to an urgent need for the development of new therapeutic approaches that can overcome the development of drug resistance. Recent evidence suggests that the biological signaling molecule carbon monoxide (CO) presents remarkable antimicrobial properties. Herein, we report the design and synthesis of a new type of water-soluble CO-releasing polymer with antimicrobial activity against Pseudomonas aeruginosa that is highly efficient at preventing biofilm formation.
Long-term effect on membrane fouling in a new membrane bioreactor as a pretreatment to seawater desalination
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.BIORTECH.2014.03.098
Abstract: Submerged membrane adsorption bio-reactors (SMABR) were investigated as a new pretreatment for seawater reverse osmosis (SWRO) desalination. They were tested with different doses of powder activated carbon (PAC) on-site for a long-term. The biofouling on the membrane was assessed in terms of DNA (cells) and polysaccharide distribution. MBR without PAC addition resulted in severe fouling on membrane. When PAC is added in the MBR, PAC could reduce the organic fouling. Hence the biofilm formation on membrane was reduced without any membrane damage. PAC also helped to remove low molecular weight (LMW) organics responsible for biofouling of RO membrane. A linear correlation between assimilable organic carbon (AOC) and LMW organics was observed. A small amount of PAC (2.4-8.0g of PAC/m(3) of seawater) was sufficient to reduce biofouling. It indicated that SMABR is an environmentally-friendly biological pretreatment to reduce biofouling for SWRO.
Recent Developments in Nitric Oxide Donors and Delivery for Antimicrobial and Anti-Biofilm Applications.
Publisher: MDPI AG
Date: 20-01-2022
DOI: 10.3390/MOLECULES27030674
Abstract: The use of nitric oxide (NO) is emerging as a promising, novel approach for the treatment of antibiotic resistant bacteria and biofilm infections. Depending on the concentration, NO can induce biofilm dispersal, increase bacteria susceptibility to antibiotic treatment, and induce cell damage or cell death via the formation of reactive oxygen or reactive nitrogen species. The use of NO is, however, limited by its reactivity, which can affect NO delivery to its target site and result in off-target effects. To overcome these issues, and enable spatial or temporal control over NO release, various strategies for the design of NO-releasing materials, including the incorporation of photo-activable, charge-switchable, or bacteria-targeting groups, have been developed. Other strategies have focused on increased NO storage and delivery by encapsulation or conjugation of NO donors within a single polymeric framework. This review compiles recent developments in NO drugs and NO-releasing materials designed for applications in antimicrobial or anti-biofilm treatment and discusses limitations and variability in biological responses in response to the use of NO for bacterial eradiation.
Nitric oxide: A key mediator of biofilm dispersal with applications in infectious diseases
Publisher: Bentham Science Publishers Ltd.
Date: 18-11-2015
DOI: 10.2174/1381612820666140905112822
Abstract: Studies of the biofilm life cycle can identify novel targets and strategies for improving biofilm control measures. Of particular interest are dispersal events, where a subpopulation of cells is released from the biofilm community to search out and colonize new surfaces. Recently, the simple gas and ubiquitous biological signaling molecule nitric oxide (NO) was identified as a key mediator of biofilm dispersal conserved across microbial species. Here, we review the role and mechanisms of NO mediating dispersal in bacterial biofilms, and its potential for novel therapeutics. In contrast to previous attempts using high dose NO aimed at killing pathogens, the use of low, non-toxic NO signals (picomolar to nanomolar range) to disperse biofilms represents an innovative and highly favourable approach to improve infectious disease treatments. Further, several NO-based technologies have been developed that offer a versatile range of solutions to control biofilms, including: (i) NO-generating compounds with short or long half-lives and safe or inert residues, (ii) novel compounds for the targeted delivery of NO to infectious biofilms during systemic treatments, and (iii) novel NO-releasing materials and surface coatings for the prevention and dispersal of biofilms. Overall the use of low levels of NO exploiting its signaling properties to induce dispersal represents an unprecedented and promising strategy for the control of biofilms in clinical and industrial contexts.
Role of quorum sensing by Pseudomonas aeruginosa in microbial keratitis and cystic fibrosis
Publisher: Microbiology Society
Date: 08-2008
DOI: 10.1099/MIC.0.2008/019281-0
Abstract: Pseudomonas aeruginosa is a ubiquitous bacterium that causes opportunistic infections in a range of host tissues and organs. Infections by P. aeruginosa are difficult to treat and hence there is interest in the development of effective therapeutics. One of the key mechanisms that P. aeruginosa uses to control the expression of many virulence factors is the N-acylated homoserine lactone (AHL) regulatory system. Hence, there is considerable interest in targeting this regulatory pathway to develop novel therapeutics for infection control. P. aeruginosa is the principal cause of microbial keratitis and of infections in cystic fibrosis (CF) sufferers, and AHL-dependent cell-to-cell signalling has been shown to be important for both infection types. However, keratitis tends to be an acute infection whereas infection of CF patients develops into a chronic, life-long infection. Thus, it is unclear whether AHL-regulated virulence plays the same role during these infections. This review presents a comparison of the role of AHL signalling in P. aeruginosa-mediated microbial keratitis and chronic lung infections of CF patients.
Indole-based novel small molecules for the modulation of bacterial signalling pathways
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4OB02096K
Abstract: Indole based N -acylated l -homoserine lactone (AHL) mimics were developed as quorum sensing (QS) inhibitors for Gram-negative bacteria Pseudomonas aeruginosa and can be used as novel antimicrobial agents.
Interactions of plasma-activated water with biofilms: inactivation, dispersal effects and mechanisms of action
Publisher: Springer Science and Business Media LLC
Date: 27-01-2021
DOI: 10.1038/S41522-020-00180-6
Abstract: Biofilms have several characteristics that ensure their survival in a range of adverse environmental conditions, including high cell numbers, close cell proximity to allow easy genetic exchange (e.g., for resistance genes), cell communication and protection through the production of an exopolysaccharide matrix. Together, these characteristics make it difficult to kill undesirable biofilms, despite the many studies aimed at improving the removal of biofilms. An elimination method that is safe, easy to deliver in physically complex environments and not prone to microbial resistance is highly desired. Cold atmospheric plasma, a lightning-like state generated from air or other gases with a high voltage can be used to make plasma-activated water (PAW) that contains many active species and radicals that have antimicrobial activity. Recent studies have shown the potential for PAW to be used for biofilm elimination without causing the bacteria to develop significant resistance. However, the precise mode of action is still the subject of debate. This review discusses the formation of PAW generated species and their impacts on biofilms. A focus is placed on the diffusion of reactive species into biofilms, the formation of gradients and the resulting interaction with the biofilm matrix and specific biofilm components. Such an understanding will provide significant benefits for tackling the ubiquitous problem of biofilm contamination in food, water and medical areas.
A rapid bioluminescence-based test of assimilable organic carbon for seawater
Publisher: Elsevier BV
Date: 05-2013
‘Big things in small packages: the genetics of filamentous phage and effects on fitness of their host’
Publisher: Oxford University Press (OUP)
Date: 10-02-2015
Abstract: This review synthesizes recent and past observations on filamentous phages and describes how these phages contribute to host phentoypes. For ex le, the CTXφ phage of Vibrio cholerae encodes the cholera toxin genes, responsible for causing the epidemic disease, cholera. The CTXφ phage can transduce non-toxigenic strains, converting them into toxigenic strains, contributing to the emergence of new pathogenic strains. Other effects of filamentous phage include horizontal gene transfer, biofilm development, motility, metal resistance and the formation of host morphotypic variants, important for the biofilm stress resistance. These phages infect a wide range of Gram-negative bacteria, including deep-sea, pressure-adapted bacteria. Many filamentous phages integrate into the host genome as prophage. In some cases, filamentous phages encode their own integrase genes to facilitate this process, while others rely on host-encoded genes. These differences are mediated by different sets of 'core' and 'accessory' genes, with the latter group accounting for some of the mechanisms that alter the host behaviours in unique ways. It is increasingly clear that despite their relatively small genomes, these phages exert signficant influence on their hosts and ultimately alter the fitness and other behaviours of their hosts.
Discovery of Cephalosporin-3′-Diazeniumdiolates That Show Dual Antibacterial and Antibiofilm Effects against Pseudomonas aeruginosa Clinical Cystic Fibrosis Isolates and Efficacy in a Murine Re
Publisher: American Chemical Society (ACS)
Date: 24-04-2020
Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria
Publisher: Springer Science and Business Media LLC
Date: 27-08-2019
DOI: 10.1038/S41522-019-0095-4
Abstract: Despite considerable research, the biofilm-forming capabilities of Nitrosomonas europaea are poorly understood for both mono and mixed-species communities. This study combined biofilm assays and molecular techniques to demonstrate that N . europaea makes very little biofilm on its own, and relies on the activity of associated heterotrophic bacteria to establish a biofilm. However, N . europaea has a vital role in the proliferation of mixed-species communities under carbon-limited conditions, such as in drinking water distribution systems, through the provision of organic carbon via ammonia oxidation. Results show that the addition of nitrification inhibitors to mixed-species nitrifying cultures under carbon-limited conditions disrupted biofilm formation and caused the dispersal of pre-formed biofilms. This dispersal effect was not observed when an organic carbon source, glucose, was included in the medium. Interestingly, inhibition of nitrification activity of these mixed-species biofilms in the presence of added glucose resulted in increased total biofilm formation compared to controls without the addition of nitrification inhibitors, or with only glucose added. This suggests that active AOB partially suppress or limit the overall growth of the heterotrophic bacteria. The experimental model developed here provides evidence that ammonia-oxidising bacteria (AOB) are involved in both the formation and maintenance of multi-species biofilm communities. The results demonstrate that the activity of the AOB not only support the growth and biofilm formation of heterotrophic bacteria by providing organic carbon, but also restrict and limit total biomass in mixed community systems.
Influence of High Intensity Focused Ultrasound on the Microstructure and c-di-GMP Signaling of Pseudomonas aeruginosa Biofilms
Publisher: Frontiers Media SA
Date: 15-12-2020
DOI: 10.3389/FMICB.2020.599407
Abstract: Bacterial biofilms are typically more tolerant to antimicrobials compared to bacteria in the planktonic phase and therefore require alternative treatment approaches. Mechanical biofilm disruption from ultrasound may be such an alternative by circumventing rapid biofilm adaptation to antimicrobial agents. Although ultrasound facilitates biofilm dispersal and may enhance the effectiveness of antimicrobial agents, the resulting biological response of bacteria within the biofilms remains poorly understood. To address this question, we investigated the microstructural effects of Pseudomonas aeruginosa biofilms exposed to high intensity focused ultrasound (HIFU) at different acoustic pressures and the subsequent biological response. Confocal microscopy images indicated a clear microstructural response at peak negative pressures equal to or greater than 3.5 MPa. In this pressure litude range, HIFU partially reduced the biomass of cells and eroded exopolysaccharides from the biofilm. These pressures also elicited a biological response we observed an increase in a biomarker for biofilm development (cyclic-di-GMP) proportional to ultrasound induced biofilm removal. Cyclic-di-GMP overproducing mutant strains were also more resilient to disruption from HIFU at these pressures. The biological response was further evidenced by an increase in the relative abundance of cyclic-di-GMP overproducing variants present in the biofilm after exposure to HIFU. Our results, therefore, suggest that both physical and biological effects of ultrasound on bacterial biofilms must be considered in future studies.
Biofilm formation and sloughing in Serratia marcescens is controlled by quorum sensing and nutrient conditions
Publisher: American Society for Microbiology
Date: 15-05-2005
DOI: 10.1128/JB.187.10.3477-3485.2005
Abstract: We describe here a role for quorum sensing in the detachment, or sloughing, of Serratia marcescens filamentous biofilms, and we show that nutrient conditions affect the biofilm morphotype. Under reduced carbon or nitrogen conditions, S. marcescens formed a classical biofilm consisting of microcolonies. The filamentous biofilm could be converted to a microcolony-type biofilm by switching the medium after establishment of the biofilm. Similarly, when initially grown as a microcolony biofilm, S. marcescens could be converted back to a filamentous biofilm by increasing the nutrient composition. Under high-nutrient conditions, an N -acyl homoserine lactone quorum-sensing mutant formed biofilms that were indistinguishable from the wild-type biofilms. Similarly, other quorum-sensing-dependent behaviors, such as swarming motility, could be rendered quorum sensing independent by manipulating the growth medium. Quorum sensing was also found to be involved in the sloughing of the filamentous biofilm. The biofilm formed by the bacterium consistently sloughed from the substratum after approximately 75 to 80 h of development. The quorum-sensing mutant, when supplemented with exogenous signal, formed a wild-type filamentous biofilm and sloughed at the same time as the wild type, and this was independent of surfactant production. When we removed the signal from the quorum-sensing mutant prior to the time of sloughing, the biofilm did not undergo significant detachment. Together, the data suggest that biofilm formation by S. marcescens is a dynamic process that is controlled by both nutrient cues and the quorum-sensing system.
Understanding, monitoring, and controlling biofilm growth in drinking water distribution systems
Publisher: American Chemical Society (ACS)
Date: 16-08-2016
Abstract: In drinking water distribution systems (DWDS), biofilms are the predominant mode of microbial growth, with the presence of extracellular polymeric substance (EPS) protecting the biomass from environmental and shear stresses. Biofilm formation poses a significant problem to the drinking water industry as a potential source of bacterial contamination, including pathogens, and, in many cases, also affecting the taste and odor of drinking water and promoting the corrosion of pipes. This article critically reviews important research findings on biofilm growth in DWDS, examining the factors affecting their formation and characteristics as well as the various technologies to characterize and monitor and, ultimately, to control their growth. Research indicates that temperature fluctuations potentially affect not only the initial bacteria-to-surface attachment but also the growth rates of biofilms. For the latter, the effect is unique for each type of biofilm-forming bacteria ammonia-oxidizing bacteria, for ex le, grow more-developed biofilms at a typical summer temperature of 22 °C compared to 12 °C in fall, and the opposite occurs for the pathogenic Vibrio cholerae. Recent investigations have found the formation of thinner yet denser biofilms under high and turbulent flow regimes of drinking water, in comparison to the more porous and loosely attached biofilms at low flow rates. Furthermore, in addition to the rather well-known tendency of significant biofilm growth on corrosion-prone metal pipes, research efforts also found leaching of growth-promoting organic compounds from the increasingly popular use of polymer-based pipes. Knowledge of the unique microbial members of drinking water biofilms and, importantly, the influence of water characteristics and operational conditions on their growth can be applied to optimize various operational parameters to minimize biofilm accumulation. More-detailed characterizations of the biofilm population size and structure are now feasible with fluorescence microscopy (epifluorescence and CLSM imaging with DNA, RNA, EPS, and protein and lipid stains) and electron microscopy imaging (ESEM). Importantly, thorough identification of microbial fingerprints in drinking water biofilms is achievable with DNA sequencing techniques (the 16S rRNA gene-based identification), which have revealed a prevalence of previously undetected bacterial members. Technologies are now moving toward in situ monitoring of biomass growth in distribution networks, including the development of optical fibers capable of differentiating biomass from chemical deposits. Taken together, management of biofilm growth in water distribution systems requires an integrated approach, starting from the treatment of water prior to entering the networks to the potential implementation of "biofilm-limiting" operational conditions and, finally, ending with the careful selection of available technologies for biofilm monitoring and control. For the latter, conventional practices, including chlorine-chloramine disinfection, flushing of DWDS, nutrient removal, and emerging technologies are discussed with their associated challenges.
Pseudomonas aeruginosadose response and bathing water infection
Publisher: Cambridge University Press (CUP)
Date: 08-11-2013
DOI: 10.1017/S0950268813002690
Abstract: Pseudomonas aeruginosa is the opportunistic pathogen mostly implicated in folliculitis and acute otitis externa in pools and hot tubs. Nevertheless, infection risks remain poorly quantified. This paper reviews disease aetiologies and bacterial skin colonization science to advance dose-response theory development. Three model forms are identified for predicting disease likelihood from pathogen density. Two are based on Furumoto & Mickey's exponential ‘single-hit’ model and predict infection likelihood and severity (lesions/m 2 ), respectively. ‘Third-generation’, mechanistic, dose-response algorithm development is additionally scoped. The proposed formulation integrates dispersion, epidermal interaction, and follicle invasion. The review also details uncertainties needing consideration which pertain to water quality, outbreaks, exposure time, infection sites, biofilms, cerumen, environmental factors (e.g. skin saturation, hydrodynamics), and whether P. aeruginosa is endogenous or exogenous. The review's findings are used to propose a conceptual infection model and identify research priorities including pool dose-response modelling, epidermis ecology and infection likelihood-based hygiene management.
In Situ Mapping of the Mechanical Properties of Biofilms by Particle-tracking Microrheology.
Publisher: MyJove Corporation
Date: 04-12-2015
DOI: 10.3791/53093
Modeling the effect of acylated homoserine lactone antagonists in Pseudomonas aeruginosa
Publisher: Elsevier BV
Date: 05-2005
DOI: 10.1016/J.BIOSYSTEMS.2004.11.008
Abstract: Pseudomonas aeruginosa is a gram-negative bacterium that causes serious illnesses, particularly in immunocompromised in iduals, often with a fatal outcome. The finding that the acylated homoserine lactone quorum sensing (QS) system controls the production of virulence factors in P. aeruginosa makes this system a possible target for antimicrobial therapy. It has been suggested that an N-(3-oxododecanoyl)-homoserine lactone (3O-C12-HSL) antagonist, a QS blocker (QSB), would interfere efficiently with the quorum sensing system in P. aeruginosa and thus reduce the virulence of this pathogen. In this work, a mathematical model of the QS system in P. aeruginosa has been developed. The model was used to virtually add 3O-C12-HSL antagonists that differed in their affinity for the receptor protein and for their ability to mediate degradation of the receptor. The model suggests that very small differences in these parameters for different 3O-C12-HSL antagonists can greatly affect the success of QSB based inhibition of the QS system in P. aeruginosa. Most importantly, it is proposed that the ability of the 3O-C12-HSL antagonist to mediate degradation of LasR is the core parameter for successful QSB based inhibition of the QS system in P. aeruginosa. Finally, this study demonstrates that QSBs can shift the system to a low steady state, corresponding to an uninduced state and thus, suggests that the use of 3O-C12-HSL antagonists may constitute a promising therapeutic approach against P. aeruginosa involved infections.
The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures
Publisher: Springer Science and Business Media LLC
Date: 19-03-2021
DOI: 10.1038/S41522-021-00197-5
Abstract: Extracellular DNA, or eDNA, is recognised as a critical biofilm component however, it is not understood how it forms networked matrix structures. Here, we isolate eDNA from static-culture Pseudomonas aeruginosa biofilms using ionic liquids to preserve its biophysical signatures of fluid viscoelasticity and the temperature dependency of DNA transitions. We describe a loss of eDNA network structure as resulting from a change in nucleic acid conformation, and propose that its ability to form viscoelastic structures is key to its role in building biofilm matrices. Solid-state analysis of isolated eDNA, as a proxy for eDNA structure in biofilms, reveals non-canonical Hoogsteen base pairs, triads or tetrads involving thymine or uracil, and guanine, suggesting that the eDNA forms G-quadruplex structures. These are less abundant in chromosomal DNA and disappear when eDNA undergoes conformation transition. We verify the occurrence of G-quadruplex structures in the extracellular matrix of intact static and flow-cell biofilms of P. aeruginosa , as displayed by the matrix to G-quadruplex-specific antibody binding, and validate the loss of G-quadruplex structures in vivo to occur coincident with the disappearance of eDNA fibres. Given their stability, understanding how extracellular G-quadruplex structures form will elucidate how P. aeruginosa eDNA builds viscoelastic networks, which are a foundational biofilm property.
Bis-(3′-5′)-Cyclic Dimeric GMP Regulates Antimicrobial Peptide Resistance in Pseudomonas aeruginosa
Publisher: American Society for Microbiology
Date: 05-2013
DOI: 10.1128/AAC.02499-12
Abstract: Bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) is an intracellular second messenger that controls the lifestyles of many bacteria. A high intracellular level of c-di-GMP induces a biofilm lifestyle, whereas a low intracellular level of c-di-GMP stimulates dispersal of biofilms and promotes a planktonic lifestyle. Here, we used the expression of different reporters to show that planktonic cells, biofilm cells, and cells dispersed from biofilms (DCells) had distinct intracellular c-di-GMP levels. Proteomics analysis showed that the low intracellular c-di-GMP level of DCells induced the expression of proteins required for the virulence and development of antimicrobial peptide resistance in Pseudomonas aeruginosa . In accordance with this, P. aeruginosa cells with low c-di-GMP levels were found to be more resistant to colistin than P. aeruginosa cells with high c-di-GMP levels. This finding contradicts the current dogma stating that dispersed cells are inevitably more susceptible to antibiotics than their sessile counterparts.
Carbon starvation of Pseudomonas aeruginosa biofilms selects for dispersal insensitive mutants
Publisher: Springer Science and Business Media LLC
Date: 22-09-2021
DOI: 10.1186/S12866-021-02318-8
Abstract: Biofilms disperse in response to specific environmental cues, such as reduced oxygen concentration, changes in nutrient concentration and exposure to nitric oxide. Interestingly, biofilms do not completely disperse under these conditions, which is generally attributed to physiological heterogeneity of the biofilm. However, our results suggest that genetic heterogeneity also plays an important role in the non-dispersing population of P. aeruginosa in biofilms after nutrient starvation. In this study, 12.2% of the biofilm failed to disperse after 4 d of continuous starvation-induced dispersal. Cells were recovered from the dispersal phase as well as the remaining biofilm. For 96 h starved biofilms, rugose small colony variants (RSCV) were found to be present in the biofilm, but were not observed in the dispersal effluent. In contrast, wild type and small colony variants (SCV) were found in high numbers in the dispersal phase. Genome sequencing of these variants showed that most had single nucleotide mutations in genes associated with biofilm formation, e.g. in wspF, pilT , fha1 and aguR . Complementation of those mutations restored starvation-induced dispersal from the biofilms. Because c-di-GMP is linked to biofilm formation and dispersal, we introduced a c-di-GMP reporter into the wild-type P. aeruginosa and monitored green fluorescent protein (GFP) expression before and after starvation-induced dispersal. Post dispersal, the microcolonies were smaller and significantly brighter in GFP intensity, suggesting the relative concentration of c-di-GMP per cell within the microcolonies was also increased. Furthermore, only the RSCV showed increased c-di-GMP, while wild type and SCV were no different from the parental strain. This suggests that while starvation can induce dispersal from the biofilm, it also results in strong selection for mutants that overproduce c-di-GMP and that fail to disperse in response to the dispersal cue, starvation.
Expression stability of 13 housekeeping genes during carbon starvation of Pseudomonas aeruginosa.
Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.MIMET.2016.06.008
Abstract: Quantitative real-time polymerase chain reaction (qRT-PCR) is a reliable technique for quantifying mRNA levels when normalised by a stable reference gene/s. Many putative reference genes are known to be affected by physiological stresses, such as nutrient limitation and hence may not be suitable for normalisation. In this study of Pseudomonas aeruginosa, the expression of 13 commonly used reference genes, rpoS, proC, recA, rpsL, rho, oprL, anr, tipA, nadB, fabD, C, algD and gyrA, were analysed for changes in expression under carbon starvation and nutrient replete conditions. The results showed that rpoS was the only stably expressed housekeeping gene during carbon starvation. In contrast, other commonly used housekeeping genes were shown to vary by as much as 10-100 fold under starvation conditions. This study has identified a suitable reference gene for qRT-PCR in P. aeruginosa during carbon starvation. The results presented here highlight the need to validate housekeeping genes under the chosen experimental conditions.
Antibiotic Resistance Characteristics of Pseudomonas aeruginosa Isolated from Keratitis in Australia and India
Publisher: MDPI AG
Date: 14-09-2020
DOI: 10.3390/ANTIBIOTICS9090600
Abstract: This study investigated genomic differences in Australian and Indian Pseudomonas aeruginosa isolates from keratitis (infection of the cornea). Overall, the Indian isolates were resistant to more antibiotics, with some of those isolates being multi-drug resistant. Acquired genes were related to resistance to fluoroquinolones, aminoglycosides, beta-lactams, macrolides, sulphonamides, and tetracycline and were more frequent in Indian (96%) than in Australian (35%) isolates (p = 0.02). Indian isolates had large numbers of gene variations (median 50,006, IQR = 26,967–50,600) compared to Australian isolates (median 26,317, IQR = 25,681–33,780). There were a larger number of mutations in the mutL and uvrD genes associated with the mismatch repair (MMR) system in Indian isolates, which may result in strains losing their efficacy for DNA repair. The number of gene variations were greater in isolates carrying MMR system genes or exoU. In the phylogenetic ision, the number of core genes were similar in both groups, but Indian isolates had larger numbers of pan genes (median 6518, IQR = 6040–6935). Clones related to three different sequence types—ST308, ST316, and ST491—were found among Indian isolates. Only one clone, ST233, containing two strains was present in Australian isolates. The most striking differences between Australian and Indian isolates were carriage of exoU (that encodes a cytolytic phospholipase) in Indian isolates and exoS (that encodes for GTPase activator activity) in Australian isolates, large number of acquired resistance genes, greater changes to MMR genes, and a larger pan genome as well as increased overall genetic variation in the Indian isolates.
Design, Synthesis and Biological Evaluation of Novel Anthraniloyl-AMP Mimics as PQS Biosynthesis Inhibitors Against Pseudomonas aeruginosa Resistance
Publisher: MDPI AG
Date: 07-07-2020
DOI: 10.3390/MOLECULES25133103
Abstract: The Pseudomonas quinolone system (PQS) is one of the three major interconnected quorum sensing signaling systems in Pseudomonas aeruginosa. The virulence factors PQS and HHQ activate the transcription regulator PqsR (MvfR), which controls several activities in bacteria, including biofilm formation and upregulation of PQS biosynthesis. The enzyme anthraniloyl-CoA synthetase (PqsA) catalyzes the first and critical step in the biosynthesis of quinolones therefore, it is an attractive target for the development of anti-virulence therapeutics against Pseudomonas resistance. Herein, we report the design and synthesis of novel triazole nucleoside-based anthraniloyl- adenosine monophosphate (AMP) mimics. These analogues had a major impact on the morphology of bacterial biofilms and caused significant reduction in bacterial aggregation and population density. However, the compounds showed only limited inhibition of PQS and did not exhibit any effect on pyocyanin production.
High bacterial diversity in nearshore and oceanic biofilms and their influence on larval settlement by Hydroides elegans (Polychaeta)
Publisher: Wiley
Date: 18-06-2019
Abstract: Settlement of many benthic marine invertebrates is stimulated by bacterial biofilms, although it is not known if patterns of settlement reflect microbial communities that are specific to discrete habitats. Here, we characterized the taxonomic and functional gene ersity (16S rRNA gene licon and metagenomic sequencing analyses), as well as the specific bacterial abundances, in biofilms from erse nearby and distant locations, both inshore and offshore, and tested them for their ability to induce settlement of the biofouling tubeworm Hydroides elegans, an inhabitant of bays and harbours around the world. We found that compositions of the bacterial biofilms were site specific, with the greatest differences between inshore and offshore sites. Further, biofilms were highly erse in their taxonomic and functional compositions across inshore sites, while relatively low ersity was found at offshore sites. Hydroides elegans settled on all biofilms tested, with settlement strongly correlated with bacterial abundance. Bacterial density in biofilms was positively correlated with biofilm age. Our results suggest that the localized distribution of H. elegans is not determined by 'selection' to locations by specific bacteria, but it is more likely linked to the prevailing local ecology and oceanographic features that affect the development of dense biofilms and the occurrence of larvae.
Sulfate-dependant microbially induced corrosion of mild steel in the deep sea: a 10-year microbiome study
Publisher: Springer Science and Business Media LLC
Date: 13-01-2022
DOI: 10.1186/S40168-021-01196-6
Abstract: Metal corrosion in seawater has been extensively studied in surface and shallow waters. However, infrastructure is increasingly being installed in deep-sea environments, where extremes of temperature, salinity, and high hydrostatic pressure increase the costs and logistical challenges associated with monitoring corrosion. Moreover, there is currently only a rudimentary understanding of the role of microbially induced corrosion, which has rarely been studied in the deep-sea. We report here an integrative study of the biofilms growing on the surface of corroding mooring chain links that had been deployed for 10 years at ~2 km depth and developed a model of microbially induced corrosion based on flux-balance analysis. We used optical emission spectrometry to analyze the chemical composition of the mooring chain and energy-dispersive X-ray spectrometry coupled with scanning electron microscopy to identify corrosion products and ultrastructural features. The taxonomic structure of the microbiome was determined using shotgun metagenomics and was confirmed by 16S licon analysis and quantitative PCR of the dsrB gene. The functional capacity was further analyzed by generating binned, genomic assemblies and performing flux-balance analysis on the metabolism of the dominant taxa. The surface of the chain links showed intensive and localized corrosion with structural features typical of microbially induced corrosion. The microbiome on the links differed considerably from that of the surrounding sediment, suggesting selection for specific metal-corroding biofilms dominated by sulfur-cycling bacteria. The core metabolism of the microbiome was reconstructed to generate a mechanistic model that combines biotic and abiotic corrosion. Based on this metabolic model, we propose that sulfate reduction and sulfur disproportionation might play key roles in deep-sea corrosion. The corrosion rate observed was higher than what could be expected from abiotic corrosion mechanisms under these environmental conditions. High corrosion rate and the form of corrosion (deep pitting) suggest that the corrosion of the chain links was driven by both abiotic and biotic processes. We posit that the corrosion is driven by deep-sea sulfur-cycling microorganisms which may gain energy by accelerating the reaction between metallic iron and elemental sulfur. The results of this field study provide important new insights on the ecophysiology of the corrosion process in the deep sea.
Evaluation of hindered amine light stabilisers and their N-chlorinated derivatives as antibacterial and antifungal additives for thermoset surface coatings
Publisher: Elsevier BV
Date: 10-2016
Nonculturability: adaptation or debilitation?
Publisher: Oxford University Press (OUP)
Date: 1998
Draft Genome Sequence of Enterobacter sp. Strain EA-1, an Electrochemically Active Microorganism Isolated from Tropical Sediment
Publisher: American Society for Microbiology
Date: 03-2018
Abstract: Enterobacter sp. strain EA-1 is an electrochemically active bacterium isolated from tropical sediment in Singapore. Here, the annotated draft genome assembly of the bacterium is reported. Whole-genome comparison indicates that Enterobacter sp. EA-1, along with a previously sequenced Enterobacter isolate from East Asia, forms a distinct clade within the Enterobacter genus.
Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing.
Publisher: Wiley
Date: 29-01-2004
DOI: 10.1111/J.1462-2920.2004.00556.X
Abstract: This study was based on the hypothesis that biofilms of the opportunistic pathogen Pseudomonas aeruginosa are successfully adapted to situations of protozoan grazing. We tested P. aeruginosa wild type and strains that were genetically altered, in structural and regulatory features of biofilm development, in response to the common surface-feeding flagellate Rhynchomonas nasuta. Early biofilms of the wild type showed the formation of grazing resistant microcolonies in the presence of the flagellate, whereas biofilms without the predator were undifferentiated. Grazing on biofilms of quorum sensing mutants (lasR and rhlR/lasR) also resulted in the formation of microcolonies, however, in lower numbers and size compared to the wild type. Considerably fewer microcolonies than the wild type were formed by mutant cells lacking type IV pili, whereas no microcolonies were formed by flagella-deficient cells. The alginate-overproducing strain PDO300 developed larger microcolonies in response to grazing. These observations suggest a role of quorum sensing in early biofilms and involvement of flagella, type IV pili, and alginate in microcolony formation in the presence of grazing. More mature biofilms of the wild type exhibited acute toxicity to the flagellate R. nasuta. Rapid growth of the flagellate on rhlR/lasR mutant biofilms indicated a key role of quorum sensing in the upregulation of lethal factors and in grazing protection of late biofilms. Both the formation of microcolonies and the production of toxins are effective mechanisms that may allow P. aeruginosa biofilms to resist protozoan grazing and to persist in the environment.
Development of antibiotic resistance in the ocular Pseudomonas aeruginosa clone ST308 over twenty years
Publisher: Elsevier BV
Date: 04-2021
Biofilms: an emergent form of bacterial life
Publisher: Springer Science and Business Media LLC
Date: 11-08-2016
Abstract: Bacterial biofilms are formed by communities that are embedded in a self-produced matrix of extracellular polymeric substances (EPS). Importantly, bacteria in biofilms exhibit a set of 'emergent properties' that differ substantially from free-living bacterial cells. In this Review, we consider the fundamental role of the biofilm matrix in establishing the emergent properties of biofilms, describing how the characteristic features of biofilms - such as social cooperation, resource capture and enhanced survival of exposure to antimicrobials - all rely on the structural and functional properties of the matrix. Finally, we highlight the value of an ecological perspective in the study of the emergent properties of biofilms, which enables an appreciation of the ecological success of biofilms as habitat formers and, more generally, as a bacterial lifestyle.
Probiotics [LGG-BB12 or RC14-GR1] versus placebo as prophylaxis for urinary tract infection in persons with spinal cord injury [ProSCIUTTU]: a randomised controlled trial
Publisher: Springer Science and Business Media LLC
Date: 27-02-2019
Biofilm development and enhanced stress resistance of a model, mixed-species community biofilm.
Publisher: Springer Science and Business Media LLC
Date: 24-10-2014
Influence of interspecies interactions on the spatial organization of dual species bacterial communities
Publisher: Elsevier BV
Date: 12-2020
Interfaces Between Bacterial and Eukaryotic Neuroecology
Publisher: Oxford University Press (OUP)
Date: 05-09-2011
DOI: 10.1093/ICB/ICR115
Abstract: The sensory capacity of bacteria and macroalgae (seaweeds) is limited with respect to many modalities (visual, auditory) common in "higher" organisms such as animals. Thus, we expect that other modalities, such as chemical signaling and sensing, would play particularly important roles in their sensory ecology. Here, we discuss two ex les of chemical signaling in bacteria and seaweeds: (1) the role of chemical defenses and quorum-sensing (QS) regulatory systems in bacterial colonization and infection of the red alga Delisea pulchra and their ecological consequences, and (2) the regulation of dispersal and differentiation by nitric oxide (NO) in bacterial biofilms. Consistent with the goals of neuroecology, in both cases, we investigate the links between specific signal-mediated molecular mechanisms, and ecological outcomes, for populations or assemblages of bacteria or seaweeds. We conclude by suggesting that because of the fundamental role played by chemical signaling in bacteria, bacterial systems, either by themselves or in interactions with other organisms, have much to offer for understanding general issues in neuroecology. Thus, further integration of microbiology with the biology of eukaryotes would seem warranted and is likely to prove illuminating.
The biofilm matrix scaffold of Pseudomonas species contains non-canonically base paired extracellular DNA and RNA
Publisher: Cold Spring Harbor Laboratory
Date: 22-01-2019
DOI: 10.1101/527267
Abstract: While extracellular DNA (eDNA) is recognized as a critical biofilm matrix component, it is not understood how it contributes to biofilm function. Here we isolate eDNA from Pseudomonas biofilms using ionic liquids, and discover that its key biophysical signatures, i.e. fluid viscoelasticity, nucleic acid conformation, and temperature and pH dependencies of gel to solution transitions, are maintained. Solid-state analysis of isolated eDNA, as a proxy for eDNA structure in biofilms, revealed non-canonical Hoogsteen base pairs, triads or tetrads involving guanine and thymine or uracil. These were less abundant in chromosomal DNA and undetected as eDNA underwent gel-sol transition. Purine-rich RNA was present in the eDNA network, which potentially enables eDNA to be the main cross-linking exopolymer in the matrix through non-canonical nucleobase interactions. Our study suggests that Pseudomonas assemble extracellular DNA and RNA into a network with viscoelastic properties, which underpin their persistence and spreading, and may aid the development of more effective controls for biofilm-associated infections.
Mechanistic action of weak acid drugs on biofilms
Publisher: Springer Science and Business Media LLC
Date: 06-07-2017
DOI: 10.1038/S41598-017-05178-3
Abstract: Selective permeability of a biofilm matrix to some drugs has resulted in the development of drug tolerant bacteria. Here we studied the efficacy of a weak organic acid drug, N-acetyl-L-cysteine (NAC), on the eradication of biofilms formed by the mucoid strain of Pseudomonas aeruginosa and investigated the commonality of this drug with that of acetic acid. We showed that NAC and acetic acid at pH pKa can penetrate the matrix and eventually kill 100% of the bacteria embedded in the biofilm. Once the bacteria are killed, the microcolonies swell in size and passively shed bacteria, suggesting that the bacteria act as crosslinkers within the extracellular matrix. Despite shedding of the bacteria, the remnant matrix remains intact and behaves as a pH-responsive hydrogel. These studies not only have implications for drug design but also offer a route to generate robust soft matter materials.
Effect of probiotics on multi-resistant organism colonisation in persons with spinal cord injury: secondary outcome of ProSCIUTTU, a randomised placebo-controlled trial
Publisher: Springer Science and Business Media LLC
Date: 17-01-2020
DOI: 10.1038/S41393-020-0420-Z
Abstract: Randomised double-blind placebo-controlled trial. Multi-resistant organism (MRO) colonisation is common in people with SCI. We aimed to determine whether Lactobacillus reuteri RC-14 + Lactobacillus GR-1 (RC14-GR1) and/or Lactobacillus rhamnosus GG + Bifidobacterium BB-12 (LGG-BB12) are effective in preventing or clearing MRO colonisation. New South Wales, Australia. The 207 SCI participants were randomised to one of four arms: (i) RC14-GR1 + LGG-BB12, (ii) RC14-GR1 + placebo, (iii) LGG-BB12 + placebo or (iv) double placebos for 6 months. Microbiological s les of nose, groin, urine and bowel were taken at baseline, 3 and 6 months. Analysis was conducted for the presence of methicillin-resistant Staphylococcus aureus (MRSA), multi-resistant gram-negative organisms (MRGNs) and vancomycin-resistant enterococcus (VRE). The outcomes were clearance of, or new colonisation with MRSA, MRGN, VRE or MROs and whether participants remained free of MRSA, MRGN, VRE or MROs throughout the study. Risk factors associated with an outcome were adjusted for using nominal or binary logistic regression. There was a significant reduction in new MRGN colonisation compared with placebo for participants treated with RC14-GR1 (OR 0.10, 95% CI, 0.01-0.88, P = 0.04), after allowing that inpatients were more likely to be newly colonised (OR 21.41, 95% CI, 3.98-115.13, P < 0.0001). Participants who intermittent self-catheterised (IMC) were more likely to remain MRO-free than those utilising SPC or IDCs (OR 2.80, 95% CI, 1.41-5.54, P = 0.009). Probiotics are ineffective at clearing MROs in people with SCI. However, RC14-GR1 is effective at preventing new colonisation with MRGNs. The use of IMC significantly improves the chance of remaining MRO-free.
Mesoscopic Energy Minimization Drives Pseudomonas aeruginosa Biofilm Morphologies and Consequent Stratification of Antibiotic Activity Based on Cell Metabolism
Publisher: American Society for Microbiology
Date: 05-2018
DOI: 10.1128/AAC.02544-17
Abstract: Segregation of bacteria based on their metabolic activities in biofilms plays an important role in the development of antibiotic resistance. Mushroom-shaped biofilm structures, which are reported for many bacteria, exhibit topographically varying levels of multiple drug resistance from the cap of the mushroom to its stalk. Understanding the dynamics behind the formation of such structures can aid in design of drug delivery systems, antibiotics, or physical systems for removal of biofilms. We explored the development of metabolically heterogeneous Pseudomonas aeruginosa biofilms using numerical models and laboratory knockout experiments on wild-type and chemotaxis-deficient mutants. We show that chemotactic processes dominate the transformation of slender and hemispherical structures into mushroom structures with a signature cap. Cellular Potts model simulation and experimental data provide evidence that accelerated movement of bacteria along the periphery of the biofilm, due to nutrient cues, results in the formation of mushroom structures and bacterial segregation. Multidrug resistance of bacteria is one of the most threatening dangers to public health. Understanding the mechanisms of the development of mushroom-shaped biofilms helps to identify the multidrug-resistant regions. We decoded the dynamics of the structural evolution of bacterial biofilms and the physics behind the formation of biofilm structures as well as the biological triggers that produce them. Combining in vitro gene knockout experiments with in silico models showed that chemotactic motility is one of the main driving forces for the formation of stalks and caps. Our results provide physicists and biologists with a new perspective on biofilm removal and eradication strategies.
Cytotoxic factor influencing acquired antimicrobial resistance in Pseudomonas aeruginosa
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/MA19048
Characterization of biofouling in a lab-scale forward osmosis membrane bioreactor (FOMBR).
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1016/J.WATRES.2014.03.052
Abstract: Forward osmosis membrane bioreactors (FOMBR) provide high quality permeate, however the propensity for membrane biofouling in FOMBRs is unknown. Here, FOMBRs were operated under high and low aeration and the membrane-associated biofilms were characterized by confocal laser scanning microscopy (CLSM) and rRNA gene-tagged pyrosequencing. CLSM images revealed that there was little biofilm formed under high aeration, while thick biofilms were observed on the membranes operated under low aeration. The ersity and richness of bacterial and archaeal communities as assessed by pyrosequencing varied under high and low aeration. The composition of the bacterial suspended sludge communities and the sessile biomass on the membrane surface, as assessed by non-metric multidimensional scaling, was significantly different under high aeration, but was more similar under low aeration. SIMPER analysis indicated that Pseudomonas, Aeromonas and Fluviicola preferentially attached to the membrane. The results presented here provide a comprehensive understanding of membrane biofouling in FOMBRs, which is essential for the development of effective control strategies.
Bacterial biofilm colonization and succession in tropical marine waters are similar across different types of stone materials used in seawall construction
Publisher: Frontiers Media SA
Date: 25-07-2022
DOI: 10.3389/FMICB.2022.928877
Abstract: Seawalls are important in protecting coastlines from currents, erosion, sea-level rise, and flooding. They are, however, associated with reduced bio ersity, due to their steep orientation, lack of microhabitats, and the materials used in their construction. Hence, there is considerable interest in modifying seawalls to enhance the settlement and ersity of marine organisms, as microbial biofilms play a critical role facilitating algal and invertebrate colonization. We assessed how different stone materials, ranging from aluminosilicates to limestone and concrete, affect biofilm formation. Metagenomic assessment of marine microbial communities indicated no significant impact of material on microbial ersity, irrespective of the erse surface chemistry and topography. Based on KEGG pathway analysis, surface properties appeared to influence the community composition and function during the initial stages of biofilm development, but this effect disappeared by Day 31. We conclude that marine biofilms converged over time to a generic marine biofilm, rather than the underlying stone substrata type playing a significant role in driving community composition.
All together now: experimental multispecies biofilm model systems.
Publisher: Wiley
Date: 2017
Abstract: Studies of microorganisms have traditionally focused on single species populations, which have greatly facilitated our understanding of the genetics and physiology that underpin microbial growth, adaptation and biofilm development. However, given that most microorganisms exist as multispecies consortia, the field is increasingly exploring microbial communities using a range of technologies traditionally limited to populations, including meta-omics based approaches and high resolution imaging. The experimental communities currently being explored range from relatively low ersity, for ex le, two to four species, to significantly more complex systems, comprised of several hundred species. Results from both defined and undefined communities have revealed a number of emergent properties, including improved stress tolerance, increased biomass production, community level signalling and metabolic cooperation. Based on results published to date, we submit that community-based studies are timely and increasingly reveal new properties associated with multispecies consortia that could not be predicted by studies of the in idual component species. Here, we review a range of defined and undefined experimental systems used to study microbial community interactions.
Quorum sensing inhibitory activities of surface immobilized antibacterial dihydropyrrolones via click chemistry
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.BIOMATERIALS.2013.11.072
Abstract: Device-related infection remains a major barrier to the use of biomaterial implants as life-saving devices. This study aims to examine the effectiveness and mechanism of action of surface attached dihydropyrrolones (DHPs), a quorum sensing (QS) inhibitor, against bacterial colonization. DHPs were covalently attached on glass surfaces via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) click reaction. The covalent attachment of DHP surfaces was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements, and the antimicrobial efficacy of the DHP coatings was assessed by confocal laser scanning microscopy (CLSM) and image analysis. The results demonstrated that covalently bound DHP compounds are effective in reducing the adhesion by up to 97% (p < 0.05) for both Pseudomonas aeruginosa and Staphylococcus aureus. Furthermore, using the green fluorescent protein (Gfp)-based reporter technology, it is demonstrated that surface attached DHPs were able to repress the expression of a lasB-gfp reporter fusion of P. aeruginosa by 72% (p < 0.001) without affecting cell viability. This demonstrates the ability of the covalently bound QS inhibitor to inhibit QS and suggests the existence of a membrane-based pathway(s) for QS inhibition. Hence, strategies based on incorporation of QS inhibitors such as DHPs represent a potential approach for prevention of device-related infections.
Novel Inhaled Combination Powder Containing Amorphous Colistin and Crystalline Rifapentine with Enhanced Antimicrobial Activities against Planktonic Cells and Biofilm of Pseudomonas aeruginosa
Publisher: American Chemical Society (ACS)
Date: 24-12-2014
DOI: 10.1021/MP500586P
Abstract: Colistin has been increasingly used for the treatment of respiratory infections caused by Gram-negative bacteria. Unfortunately parenteral administration of colistin can cause severe adverse effects. This study aimed to develop an inhaled combination dry powder formulation of colistin and rifapentine for the treatment of respiratory infections. The combination formulation was produced by spray-drying rifapentine particles suspended in an aqueous colistin solution. The combination dry powder had enhanced antimicrobial activities against planktonic cells and biofilm cultures of Pseudomonas aeruginosa, with both minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC) values (2 and 4 mg/L, respectively) being half that of pure colistin (MIC 4 mg/L and MBIC 8 mg/L) and 1/16th that of pure rifapentine (MIC 32 mg/L and MBIC 64 mg/L). High aerosol performance, as measured via an Aerolizer device, was observed with emitted doses>89% and fine particle fraction (FPF) total>76%. The proportion of submicron particles of rifapentine particles was minimized by the attachment of colistin, which increased the overall particle mass and aerodynamic size distribution. Using the spray-drying method described here, stable particles of amorphous colistin and crystalline rifapentine were distributed homogeneously in each stage of the impinger. Unlike the colistin alone formulation, no deterioration in aerosol performance was found for the combination powder when exposed to a high relative humidity of 75%. In our previous study, surface coating by rif icin contributed to the moisture protection of colistin. Here, a novel approach with a new mechanism was proposed whereby moisture protection was attributed to the carrier effect of elongated crystalline rifapentine particles, which minimized contact between hygroscopic colistin particles. This inhaled combination antibiotic formulation with enhanced aerosol dispersion efficiency and in vitro efficacy could become a superior treatment for respiratory infections.
Diversity of retron elements in a population of rhizobia and other gram-negative bacteria.
Publisher: American Society for Microbiology
Date: 07-1993
DOI: 10.1128/JB.175.13.4250-4254.1993
Abstract: Genetic elements called retrons reside on the chromosome of Escherichia coli and the myxobacteria and represent the first reverse transcriptase-encoding element to be found in a prokaryotic cell. All known retrons produce a functionally obscure RNA-DNA satellite molecule called multicopy single-stranded DNA (msDNA). We report here the presence of msDNA-producing retron elements in a number of new bacterial groups, including strains of the genera Proteus, Klebsiella, Salmonella, Nannocystis, Rhizobium, and Bradyrhizobium. Among a population of 63 rhizobia strains, only 16% contain a retron element. The rhizobia retrons appear to be heterogeneous in nucleotide sequence and show little similarity to previously studied retrons of E. coli and the myxobacteria.
Microbial Predation Accelerates Granulation and Modulates Microbial Community Composition
Publisher: Research Square Platform LLC
Date: 19-01-2021
DOI: 10.21203/RS.3.RS-146426/V1
Abstract: Background Bacterial communities are responsible for biological nutrient removal and flocculation in engineered systems such as activated floccular sludge. Predators such as bacteriophage and protozoa exert significant predation pressure and cause bacterial mortality within these communities. However, the roles of bacteriophage and protozoan predation in impacting granulation process remain limited. Recent studies hypothesised that protozoa, particularly sessile ciliates, could have an important role in granulation as these ciliates were often observed in high abundance on surfaces of granules. Bacteriophages were hypothesized to contribute to granular stability through bacteriophage-mediated extracellular DNA release by lysing bacterial cells. This current study investigated the bacteriophage and protozoan communities throughout the granulation process. In addition, the importance of protozoan predation during granulation was also determined through chemical killing of protozoa in the floccular sludge. Results Four independent bioreactors seeded with activated floccular sludge were operated for aerobic granulation for 11 weeks. Changes in the phage, protozoa and bacterial communities were characterized throughout the granulation process. The filamentous phage, Inoviridae, increased in abundance at the initiation phase of granulation. However, the abundance shifted towards lytic phages during the maturation phase. In contrast, the abundance and ersity of protozoa decreased initially, possibly due to the reduction in settling time and subsequent washout. Upon the formation of granules, ciliated protozoa from the class Oligohymenophorea were the dominant group of protozoa based on metacommunity analysis. These protozoa had a strong, positive-correlation with the initial formation of compact aggregates prior to granule development. Furthermore, chemical inhibition of these ciliates in the floccular sludge delayed the initiation of granule formation. Analysis of the bacterial communities in the thiram treated sludge demonstrated that the recovery of ‘ Candidatus Accmulibacter’ was positively correlated with the formation of compact aggregates and granules. Conclusion Predation by bacteriophage and protozoa were positively correlated with the formation of aerobic granules. Increases in Inoviridae abundance suggested that filamentous phages may promote the structural formation of granules. Initiation of granules formation was delayed due to an absence of protozoa after chemical treatment. The presence of Candidatus Accumulibacter was necessary for the formation of granules in the absence of protozoa.
Quorum Sensing-Controlled Biofilm Development in Serratia liquefaciens MG1
Publisher: American Society for Microbiology
Date: 02-2004
DOI: 10.1128/JB.186.3.692-698.2004
Abstract: Serratia liquefaciens MG1 contains an N- acylhomoserine lactone-mediated quorum-sensing system that is known to regulate swarming motility colonization. In this study, we describe for S. liquefaciens MG1 the development of a novel biofilm consisting of cell aggregates and differentiated cell types, such as cell chains and long filamentous cells. Furthermore, quorum sensing is shown to be crucial for normal biofilm development and for elaborate differentiation. A mutant of S. liquefaciens MG1 that was incapable of synthesizing extracellular signal formed a thin and nonmature biofilm lacking cell aggregates and differentiated cell chains. Signal-based complementation of this mutant resulted in a biofilm with the wild-type architecture. Two quorum-sensing-regulated genes ( bsmA and bsmB ) involved in biofilm development were identified, and we propose that these genes are engaged in fine-tuning the formation of cell aggregates at a specific point in biofilm development.
A risk assessment of Pseudomonas aeruginosa in swimming pools: a review
Publisher: IWA Publishing
Date: 14-05-2012
DOI: 10.2166/WH.2012.020
Abstract: Despite routine monitoring and disinfection, treated swimming pools are frequently contaminated with the opportunistic pathogen Pseudomonas aeruginosa, which can represent a significant public health threat. This review was undertaken to identify the current understanding of risk factors associated with pool operation with respect to P. aeruginosa. The ecology and factors that promote growth of P. aeruginosa in the pool environment are complex and dynamic and so we applied a systematic risk assessment approach to integrate existing data, with the aim to improve pool management and safety. Sources of P. aeruginosa, types of infections, dose responses, routes of transmission, as well as the efficacy of current disinfectant treatments were reviewed. This review also highlights the critical knowledge gaps that are required for a more robust, quantitative risk assessment of P. aeruginosa. Quantitative risk management strategies have been successfully applied to drinking water systems and should similarly be amenable to developing a better understanding of the risk posed by P. aeruginosa in swimming pools.
[12] Genetic and chemical tools for investigating signaling processes in biofilms
Publisher: Elsevier
Date: 2001
A programmable lipid-polymer hybrid nanoparticle system for localized, sustained antibiotic delivery to Gram-positive and Gram-negative bacterial biofilms
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7NH00167C
Abstract: Lipid-polymer hybrid nanoparticle enhances antibiotic efficacy through localised, sustained delivery to bacterial biofilms.
The SiaABC threonine phosphorylation pathway controls biofilm formation in response to carbon availability inPseudomonas aeruginosa
Publisher: Cold Spring Harbor Laboratory
Date: 19-06-2019
DOI: 10.1101/674879
Abstract: The critical role of bacterial biofilms in chronic human infections calls for novel anti-biofilm strategies targeting the regulation of biofilm development. However, the regulation of biofilm development is very complex and can include multiple, highly interconnected signal transduction/response pathways, which are incompletely understood. We demonstrated previously that in the opportunistic, human pathogen P. aeruginosa , the PP2C-like protein phosphatase SiaA and the di-guanylate cyclase SiaD control the formation of macroscopic cellular aggregates, a type of suspended biofilms, in response to surfactant stress. In this study, we demonstrate that the SiaABC proteins represent a signal response pathway that functions through a partner switch mechanism to control biofilm formation. We also demonstrate that SiaABCD functionality is dependent on carbon substrate availability for a variety of substrates, and that upon carbon starvation, SiaB mutants show impaired dispersal, in particular with the primary fermentation product ethanol. This suggests that carbon availability is at least one of the key environmental cues integrated by the SiaABCD system. Further, our biochemical, physiological and crystallographic data reveals that the phosphatase SiaA and its kinase counterpart SiaB balance the phosphorylation status of their target protein SiaC at threonine 68 (T68). Crystallographic analysis of the SiaA-PP2C domain shows that SiaA is present as a dimer. Dynamic modelling of SiaA with SiaC suggested that SiaA interacts strongly with phosphorylated SiaC and dissociates rapidly upon dephosphorylation of SiaC. Further, we show that the known phosphatase inhibitor fumonisin inhibits SiaA mediated phosphatase activity in vitro . In conclusion, the present work improves our understanding of how P. aeuruginosa integrates specific environmental conditions, such as carbon availability and surfactant stress, to regulate cellular aggregation and biofilm formation. With the biochemical and structural characterization of SiaA, initial data on the catalytic inhibition of SiaA, and the interaction between SiaA and SiaC, our study identifies promising targets for the development of biofilm-interference drugs to combat infections of this aggressive opportunistic pathogen. Pseudomonas aeruginosa is a Gram-negative bacterium that is feared within clinical environments due to its potential to cause life-threatening acute and chronic infections. One cornerstone of its success is the ability to form and disperse from biofilms, which are self-made, multicellular structures that protect the in idual cell from the human immune system and antibiotic treatment. As such, therapies that combine a biofilm-interference strategy and the use of antimicrobial drugs represent one of the promising strategies to tackle infections of this organism. With the current study, we gain a deeper understanding of the SiaABCD mediated biofilm formation in response to clinically relevant environmental conditions. Further, our structural and biochemical characterization of the PP2C-type protein-phosphatase SiaA and the partner switch protein SiaC suggest that both represent promising novel targets for the development of future anti-biofilms drugs based on a signal interference strategy.
WILLCOX,WALTER,FRANCIS - MARCH 22, 1861 - OCTOBER 30, 1964
Publisher: Informa UK Limited
Date: 12-1964
Low-Dose Nitric Oxide as Targeted Anti-biofilm Adjunctive Therapy to Treat Chronic Pseudomonas aeruginosa Infection in Cystic Fibrosis
Publisher: Elsevier BV
Date: 09-2017
Phylogenetic comparison of retron elements among the myxobacteria: evidence for vertical inheritance.
Publisher: American Society for Microbiology
Date: 1995
DOI: 10.1128/JB.177.1.37-45.1995
Abstract: Twenty-eight myxobacterial strains, representing members from all three subgroups, were screened for the presence of retron elements, which are novel prokaryotic retroelements encoding reverse transcriptase. The presence of retrons was determined by assaying strains for a small satellite DNA produced by reverse transcription called multicopy, single-stranded DNA (msDNA). An msDNA-producing retron appeared to be absent from only one of the strains surveyed. DNA hybridization experiments revealed that retron elements similar to retron Mx162, first identified in Myxococcus xanthus, were found only among members of the Myxococcus subgroup that is, each of the seven different genera which constitute this subgroup contained a Mx162 homolog. Another retron element also appeared to have a clustered distribution, being found exclusively within the Nannocystis subgroup of the myxobacteria. A retron element of the Mx162 type was cloned from Melittangium lichenicola, and its DNA sequence was compared with those of similar elements in M. xanthus and Stigmatella aurantiaca. Together, the degree of sequence ersity, the codon bias of the reverse transcriptase genes, and the clustered distribution of these retrons suggest a possible evolutionary scenario in which a common ancestor of the Myxococcus subgroup may have acquired this retroelement.
Synthesis, quorum sensing inhibition and docking studies of 1,5-dihydropyrrol-2-ones
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.BMC.2015.10.025
Abstract: Gram-negative bacteria such as Pseudomonas aeruginosa and Escherichia coli use N-acylated l-homoserine lactones (AHLs) as autoinducers (AIs) for quorum sensing (QS), a chief regulatory and cell-to-cell communication system. QS is responsible for social adaptation, virulence factor production, biofilm production and antibiotic resistance in bacteria. Fimbrolides, a class of halogenated furanones isolated from the red marine alga Delisea pulchra, have been shown to exhibit promising QS inhibitory activity against various Gram-negative and Gram-positive bacterial strains. In this work, various lactam analogues of fimbrolides viz., 1,5-dihydropyrrol-2-ones, were designed and synthesized via an efficient lactamization protocol. All the synthesized analogues were tested for QS inhibition against the E. coli AHL-monitor strain JB357 gfp (ASV). Compound 17a emerged as the most potent compound, followed by 9c, with AIC40 values (the ratio of synthetic inhibitor to natural AHL signaling molecule that is required to lower GFP expression to 40%) of 1.95 and 19.00, respectively. Finally, the potential binding interactions between the synthesized molecules and the LasR QS receptor were studied by molecular docking. Our results indicate that 1,5-dihydropyrrol-2-ones have the ability to serve as potential leads for the further development of novel QS inhibitors as antimicrobial therapeutics.
Biofilm dispersal cells of a cystic fibrosis Pseudomonas aeruginosa isolate exhibit variability in functional traits likely to contribute to persistent infection
Publisher: Oxford University Press (OUP)
Date: 11-2012
Association between possession of ExoU and antibiotic resistance in pseudomonas aeruginosa
Publisher: Public Library of Science (PLoS)
Date: 28-09-2018
Nanosilver and the microbiological activity of the particulate solids versus the leached soluble silver
Publisher: Informa UK Limited
Date: 15-02-2018
DOI: 10.1080/17435390.2018.1434910
Abstract: Nanosilver (Ag NPs) is currently one of the most commercialized antimicrobial nanoparticles with as yet, still unresolved cytotoxicity origins. To date, research efforts have mostly described the antimicrobial contribution from the leaching of soluble silver, while the undissolved solid Ag particulates are often considered as being microbiologically inert, serving only as source of the cytotoxic Ag ions. Here, we show the rapid stimulation of lethal cellular oxidative stress in bacteria by the presence of the undissolved Ag particulates. The cytotoxicity characteristics are distinct from those arising from the leached soluble Ag, the latter being locked in organic complexes. The work also highlights the unique oxidative stress-independent bacterial toxicity of silver salt. Taken together, the findings advocate that future enquiries on the antimicrobial potency and also importantly, the environmental and clinical impact of Ag NPs use, should pay attention to the potential bacterial toxicological responses to the undissolved Ag particulates, rather than just to the leaching of soluble silver. The findings also put into question the common use of silver salt as model material for evaluating bacterial toxicity of Ag NPs.
REMOVED: Bio-Inspired Enhancement of Membrane Desalination
Publisher: Elsevier BV
Date: 2012
Design, Synthesis, and Evaluation of Fimbrolide–Nitric Oxide Donor Hybrids as Antimicrobial Agents
Publisher: American Chemical Society (ACS)
Date: 21-11-2013
DOI: 10.1021/JM400951F
Abstract: Fimbrolides from marine algae have shown promising activity against quorum sensing (QS), a chief regulatory and communication system in bacteria controlling biofilm formation and virulence factor. Nitric oxide (NO) at sublethal concentration has also been reported to induce dispersal of bacterial biofilms and increase their susceptibility toward standard biocides and antibiotics. Therefore, the combination of QS inhibitors and NO donors has the potential to control the development of biofilm and promote their dispersion via a nonbactericidal mechanism. Inspired by these ideas, novel fimbrolide-NO donor hybrid compounds were designed and synthesized. Fimbrolide-NO hybrids 6b, 6f, and 14a were found to be particularly effective as antimicrobials compared to the nonhybrid natural fimbrolides as revealed by bioluminescent P. aeruginosa QS reporter assays and biofilm inhibition assays. Significantly, these fimbrolide-NO hybrids represent the first dual-action antimicrobial agent based on the baterial QS inhibition and NO signaling.
Accessory genome contributes to the virulence and resistance of the ocular isolate of Pseudomonas aeruginosa: A complete genome analysis
Publisher: Cold Spring Harbor Laboratory
Date: 17-12-2018
DOI: 10.1101/497974
Abstract: Bacteria can acquire an accessory genome through the horizontal transfer of genetic elements from non-parental lineages. This leads to rapid genetic evolution allowing traits such as antibiotic resistance and virulence to spread through bacterial communities. The study of complete genomes of bacterial strains helps to understand the genomic traits associated with virulence and antibiotic resistance. We aimed to investigate the complete accessory genome of an ocular isolate of P. aeruginosa. We obtained the complete genome of the ocular isolate strain PA34 of P. aeruginosa utilising genome sequence reads from Illumina and Oxford Nanopore Technology followed by PCR to close any identified gaps. In-depth genomic analysis was performed using various bioinformatics tools. The phenotypic properties of susceptibility to heavy metals and cytotoxicity were determined to confirm expression of certain traits. The complete genome of PA34 includes a chromosome of 6.8 Mbp and two plasmids of 95.4 Kbp (pMKPA34-1) and 26.8 Kbp (pMKPA34-2). PA34 had a large accessory genome of 1,213 genes and had 543 unique genes not present in other strains. These exclusive genes encoded features related to metal and antibiotic resistance, phage integrase and transposons. At least 24 GIs were predicated in the complete chromosome, of which two were integrated into novel sites. Eleven GIs carried virulence factors or replaced pathogenic genes. A bacteriophage carried the aminoglycoside resistance gene (aac(3)-IId). The two plasmids carried other six antibiotic resistance genes. The large accessory genome of this ocular isolate plays a large role in shaping its virulence and antibiotic resistance.
Grazing resistance of Pseudomonas aeruginosa biofilms depends on type of protective mechanism, developmental stage and protozoan feeding mode.
Publisher: Wiley
Date: 15-07-2005
DOI: 10.1111/J.1462-2920.2005.00851.X
Abstract: In a previous study we identified microcolony formation and inhibitor production as the major protective mechanisms of Pseudomonas aeruginosa biofilms against flagellate grazing. Here we compared the efficacy of these two key protective mechanisms by exposing biofilms of the non-toxic alginate overproducing strain PDO300 and the wild-type toxic strain PAO1 to a range of feeding types commonly found in the succession of protozoans associated with natural biofilms. Alginate-mediated microcolony formation conferred effective protection for strain PDO300 against the suspension feeding flagellate Bodo saltans and, as reported earlier, the surface feeding flagellate Rhynchomonas nasuta, both of which are considered as early biofilm colonizers. However, microcolonies of mature PDO300 biofilms were highly susceptible to late biofilm colonizers, the surface-feeding amoeba Acanthamoeba polyphaga and the planktonic ciliate Tetrahymena sp., resulting in a significant reduction of biofilm biomass. Mature biofilms of strain PAO1 inhibited growth of flagellates and A. polyphaga while the grazing activity of Tetrahymena sp. remained unaffected. Our findings suggest that inhibitor production of mature P. aeruginosa biofilms is effective against a wider range of biofilm-feeding predators while microcolony-mediated protection is only beneficial in the early stages of biofilm formation.
Weak acids as an alternative anti-microbial therapy
Publisher: Elsevier BV
Date: 12-2020
Investigation of the microbial communities colonizing prepainted steel used for roofing and walling
Publisher: Wiley
Date: 20-12-2017
DOI: 10.1002/MBO3.425
The impact of flux and spacers on biofilm development on reverse osmosis membranes
Publisher: Elsevier BV
Date: 07-2012
Nitric oxide-mediated dispersal in single- and multi-species biofilms of clinically and industrially relevant microorganisms
Publisher: Wiley
Date: 17-04-2009
Quorum quenching bacteria can be used to inhibit the biofouling of reverse osmosis membranes
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.WATRES.2017.01.028
Abstract: Over the last few decades, significant efforts have concentrated on mitigating biofouling in reverse osmosis (RO) systems, with a focus on non-toxic and sustainable strategies. Here, we explored the potential of applying quorum quenching (QQ) bacteria to control biofouling in a laboratory-scale RO system. For these experiments, Pantoea stewartii was used as a model biofilm forming organism because it was previously shown to be a relevant wastewater isolate that also forms biofilms in a quorum sensing (QS) dependent fashion. A recombinant Escherichia coli strain, which can produce a QQ enzyme, was first tested in batch biofilm assays and significantly reduced biofilm formation by P. stewartii. Subsequently, RO membranes were fouled with P. stewartii and the QQ bacterium was introduced into the RO system using two different strategies, direct injection and immobilization within a cartridge microfilter. When the QQ bacterial cells were directly injected into the system, N-acylhomoserine lactone signals were degraded, resulting in the reduction of biofouling. Similarly, the QQ bacteria controlled biofouling when immobilized within a microfilter placed downstream of the RO module to remove QS signals circulating in the system. These results demonstrate the proof-of-principle that QQ can be applied to control biofouling of RO membranes and may be applicable for use in full-scale plants.
Measurement of oxygen concentrations in bacterial biofilms using transient state monitoring by single plane illumination microscopy
Publisher: IOP Publishing
Date: 06-06-2017
Theoretical Study of Molecular Determinants Involved in Signal Binding to the TraR Protein of Agrobacterium tumefaciens
Publisher: MDPI AG
Date: 31-10-2005
DOI: 10.3390/10101263
Draft Genome Sequence of Klebsiella pneumoniae Strain KP-1.
Publisher: American Society for Microbiology
Date: 26-12-2013
Abstract: Klebsiella pneumoniae is ubiquitous in the environment and is a member of a three-species biofilm model. We compared the genome sequence of an environmental isolate, K. pneumoniae strain KP-1, to those of two clinical strains (NTUH-K2044 and MGH 78578). KP-1 possesses strain-specific prophage sequences that distinguish it from the clinical strains.
The ratio of nicotinic acid to nicotinamide as a microbial biomarker for assessing cell therapy product sterility
Publisher: Elsevier BV
Date: 06-2022
Convection and the Extracellular Matrix Dictate Inter- and Intra-Biofilm Quorum Sensing Communication in Environmental Systems
Publisher: American Chemical Society (ACS)
Date: 10-05-2020
Study linking enteroviral infection with motor neurone disease is not confirmed.
Publisher: BMJ
Date: 22-11-1997
DOI: 10.1136/BMJ.315.7119.1380
Abstract: The purpose of this study was to quantitatively assess Achilles tendon mechanical behavior during gait in children with cerebral palsy (CP). We used a newly designed noninvasive sensor to measure Achilles tendon force in 11 children with CP (4F, 8-16 years old) and 15 typically developing children (controls) (9F, 8-17 years old) during overground walking. Mechanical work loop plots (force-displacement plots) were generated by combining muscle-tendon kinetics, kinematics, and EMG activity to evaluate the Achilles tendon work generated about the ankle. Work loop patterns in children with CP were substantially different than those seen in controls. Notably, children with CP showed significantly diminished work production at their preferred speed compared to controls at their preferred speed and slower speeds. Despite testing a heterogeneous population of children with CP, we observed a homogenous spring-like muscle-tendon behavior in these participants. This is in contrast with control participants who used their plantar flexors like a motor during gait. Statement of Clinical Significance: These data demonstrate the potential for using skin-mounted sensors to objectively evaluate muscle contributions to work production in pathological gait.
Thioether-linked dihydropyrrol-2-one analogues as PqsR antagonists against antibiotic resistant Pseudomonas aeruginosa
Publisher: Elsevier BV
Date: 02-2021
Mechanical signatures of microbial biofilms in micropillar-embedded growth chambers
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SM02755A
Abstract: Biofilms are surface-attached communities of microorganisms embedded in an extracellular matrix and are essential for the cycling of organic matter in natural and engineered environments.
Cephalosporin-3'-diazeniumdiolates: targeted NO-donor prodrugs for dispersing bacterial biofilms.
Publisher: Wiley
Date: 13-08-2012
Dispersal from Microbial Biofilms.
Publisher: American Society for Microbiology
Date: 18-12-2015
DOI: 10.1128/MICROBIOLSPEC.MB-0015-2014
Abstract: One common feature of biofilm development is the active dispersal of cells from the mature biofilm, which completes the biofilm life cycle and allows for the subsequent colonization of new habitats. Dispersal is likely to be critical for species survival and appears to be a precisely regulated process that involves a complex network of genes and signal transduction systems. Sophisticated molecular mechanisms control the transition of sessile biofilm cells into dispersal cells and their coordinated detachment and release in the bulk liquid. Dispersal cells appear to be specialized and exhibit a unique phenotype different from biofilm or planktonic bacteria. Further, the dispersal population is characterized by a high level of heterogeneity, reminiscent of, but distinct from, that in the biofilm, which could potentially allow for improved colonization under various environmental conditions. Here we review recent advances in characterizing the molecular mechanisms that regulate biofilm dispersal events and the impact of dispersal in a broader ecological context. Several strategies that exploit the mechanisms controlling biofilm dispersal to develop as applications for biofilm control are also presented.
Phenotypic diversification and adaptation of Serratia marcescens MG1 biofilm-derived morphotypes
Publisher: American Society for Microbiology
Date: 2007
DOI: 10.1128/JB.00930-06
Abstract: We report here the characterization of dispersal variants from microcolony-type biofilms of Serratia marcescens MG1. Biofilm formation proceeds through a reproducible process of attachment, aggregation, microcolony development, hollow colony formation, and dispersal. From the time when hollow colonies were observed in flow cell biofilms after 3 to 4 days, at least six different morphological colony variants were consistently isolated from the biofilm effluent. The timing and pattern of variant formation were found to follow a predictable sequence, where some variants, such as a smooth variant with a sticky colony texture (SSV), could be consistently isolated at the time when mature hollow colonies were observed, whereas a variant that produced copious amounts of capsular polysaccharide (SUMV) was always isolated at late stages of biofilm development and coincided with cell death and biofilm dispersal or sloughing. The morphological variants differed extensively from the wild type in attachment, biofilm formation, and cell ultrastructure properties. For ex le, SSV formed two- to threefold more biofilm biomass than the wild type in batch biofilm assays, despite having a similar growth rate and attachment capacity. Interestingly, the SUMV, and no other variants, was readily isolated from an established SSV biofilm, indicating that the SUMV is a second-generation genetic variant derived from SSV. Planktonic cultures showed significantly lower frequencies of variant formation than the biofilms (5.05 × 10 −8 versus 4.83 × 10 −6 , respectively), suggesting that there is strong, ersifying selection occurring within biofilms and that biofilm dispersal involves phenotypic radiation with ergent phenotypes.
Probiotics [LGG-BB12 or RC14-GR1] versus placebo as prophylaxis for urinary tract infection in persons with spinal cord injury [ProSCIUTTU]: a study protocol for a randomised controlled trial
Publisher: Springer Science and Business Media LLC
Date: 16-04-2016
Using Diphenylphosphoryl Azide (DPPA) for the Facile Synthesis of Biodegradable Antiseptic Random Copolypeptides
Publisher: Wiley
Date: 07-02-2017
Abstract: A facile method has been developed for the large-scale synthesis of random copolypeptides composed of multiple (i.e., cationic, hydrophobic, and hydrophilic) amino acids and their relative ratios have been optimized for broad-spectrum antibacterial effect. The copolypeptides obtained have measured compositions close to the design ratios in spite of the differing reactivities of the different amino acids. An optimized random copolypeptide of lysine, leucine, and serine (denoted as KLS-3) mimicking the composition of LL-37 host defense peptide gives broad spectrum antibacterial activity against clinically relevant Gram-negative and Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO1) with minimum inhibitory concentrations (MICs) of 32-64 μg mL
Starvation Response of the Marine Barophile CNPT-3.
Publisher: American Society for Microbiology
Date: 08-1992
DOI: 10.1128/AEM.58.8.2432-2437.1992
Abstract: The psychrophilic marine barophile CNPT-3 underwent a starvation-survival response similar to that reported for the marine bacteria Ant-300, DW1, and S-14. The number of culturable cells increased initially and then decreased gradually over a 24-day starvation period, with corresponding decreases in total cell number and direct viability count. A significant reduction in cell size and biovolume accompanied these changes. Starved cells demonstrated a greater tendency to attach at the in situ pressure (400 atm ca. 40.5 MPa) and temperature (5°C) than at 1 atm (ca. 101 kPa), and the extent of attachment increased with increasing duration of starvation. The membrane fatty acid profile of the marine barophile CNPT-3 was studied as the cells were subjected to starvation conditions. A 37.5% increase in saturated fatty acids was observed during the first 8 days of starvation, with a concomitant decrease in unsaturated fatty acids. There was also an increase in the amount of short-chain ( C 15:0 ) fatty acids.
Dynamic modelling of cell death during biofilm development
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.JTBI.2011.10.007
Abstract: Biofilms are currently recognised as the predominant bacterial life-style and it has been suggested that biofilm development is influenced by a number of different processes such as adhesion, detachment, mass transport, quorum sensing, cell death and active dispersal. One of the least understood processes and its effects on biofilm development is cell death. However, experimental studies suggest that bacterial death is an important process during biofilm development and many studies show a relationship between cell death and dispersal in microbial biofilms. We present a model of the process of cell death during biofilm development, with a particular focus on the spatial localisation of cell death or cell damage. Three rules governing cell death or cell damage were evaluated which compared the effects of starvation, damage accumulation, and viability during biofilm development and were also used to design laboratory based experiments to test the model. Results from model simulations show that actively growing biofilms develop steep nutrient gradients within the interior of the biofilm that affect neighbouring microcolonies resulting in cell death and detachment. Two of the rules indicated that high substrate concentrations lead to accelerated cell death, in contrast to the third rule, based on the accumulation of damage, which predicted earlier cell death for biofilms grown with low substrate concentrations. Comparison of the modelling results with experimental results suggests that cell death is favoured under low nutrient conditions and that the accumulation of damage may be the main cause of cell death during biofilm development.
Adaptation to an Amoeba Host Leads to Pseudomonas aeruginosa Isolates with Attenuated Virulence
Publisher: American Society for Microbiology
Date: 08-03-2022
DOI: 10.1128/AEM.02322-21
Abstract: Pseudomonas aeruginosa is an opportunistic pathogen that causes both acute infections in plants and animals, including humans, and chronic infections in immunocompromised and cystic fibrosis patients. This bacterium is commonly found in soils and water, where bacteria are constantly under threat of being consumed by bacterial predators, e.g., protozoa.
Acquired fluoroquinolone resistance genes in corneal isolates of Pseudomonas aeruginosa
Publisher: Cold Spring Harbor Laboratory
Date: 21-05-2020
DOI: 10.1101/2020.05.17.100396
Abstract: Fluroquinolones are widely used as an empirical therapy for pseudomonal ocular infections. Based on increasing reports on acquired fluroquinolone resistance genes in clinical isolates of Pseudomonas aeruginosa , we investigated 33 strains of P. aeruginosa isolated from the cornea of microbial keratitis patients in India and Australia between 1992 and 2018 to understand the prevalence of acquired fluroquinolone resistance genes in ocular isolates and to assess whether the possession of those genes was associated with fluoroquinolone susceptibility. We obtained the whole genome sequence of 33 isolates using Illumina MiSeq platform and investigated the prevalence of two fluoroquinolone resistance genes crpP and qnrVC1 . To examine the associated mobile genetic elements of qnrVC1 positive strains, we obtained long read sequences using Oxford Nanopore MinION and performed hybrid assembly to combine long reads with Illumina short sequence reads. We further assessed mutations in QRDRs and antibiotic susceptibilities to ciprofloxacin, levofloxacin and moxifloxacin to examine the association between resistance genes and phenotype. Twenty strains possessed crpP in genetic islands characterised by possession of integrative conjugative elements. The qnrVC1 gene was carried by four isolates on class I integrons and Tn 3 transposons along with aminoglycoside and beta-lactam resistance genes. We did not observe any evidence of plasmids carrying fluroquinolone resistance genes. Resistance to fluroquinolones was observed in those strains which possessed crpP, qnrVC1 and that had QRDRs mutations. The presence of crpP was not a sole cause of fluroquinolone resistance.
Immobilization of Antibacterial Dihydropyrrol-2-ones on Functional Polymer Supports To Prevent Bacterial Infections In Vivo
Publisher: American Society for Microbiology
Date: 02-2012
DOI: 10.1128/AAC.05814-11
Abstract: Antibiotic-resistant Staphylococcus aureus is of great concern, as it causes a wide range of life-threatening infections. The current study demonstrates that dihydropyrrolone (DHP)-coated polyacrylamide substrates are effective in reducing the number of culturable clinical isolates of S. aureus in vitro in a dose-dependent manner and are able to reduce the pathogenic potential of staphylococcal infection in a subcutaneous infection model. Covalently bound DHPs therefore show great potential for use as an antimicrobial strategy in device-related applications.
Comparative genomics of clinical strains of Pseudomonas aeruginosa strains isolated from different geographic sites
Publisher: Springer Science and Business Media LLC
Date: 23-10-2018
DOI: 10.1038/S41598-018-34020-7
Abstract: The large and complex genome of Pseudomonas aeruginosa , which consists of significant portions (up to 20%) of transferable genetic elements contributes to the rapid development of antibiotic resistance. The whole genome sequences of 22 strains isolated from eye and cystic fibrosis patients in Australia and India between 1992 and 2007 were used to compare genomic ergence and phylogenetic relationships as well as genes for antibiotic resistance and virulence factors. Analysis of the pangenome indicated a large variation in the size of accessory genome amongst 22 stains and the size of the accessory genome correlated with number of genomic islands, insertion sequences and prophages. The strains were erse in terms of sequence type and dissimilar to that of global epidemic P . aeruginosa clones. Of the eye isolates, 62% clustered together within a single lineage. Indian eye isolates possessed genes associated with resistance to aminoglycoside, beta-lactams, sulphonamide, quaternary ammonium compounds, tetracycline, trimethoprims and chlor henicols. These genes were, however, absent in Australian isolates regardless of source. Overall, our results provide valuable information for understanding the genomic ersity of P . aeruginosa isolated from two different infection types and countries.
Design and Synthesis of Lactams Derived from Mucochloric and Mucobromic Acids as Pseudomonas aeruginosa Quorum Sensing Inhibitors
Publisher: MDPI AG
Date: 07-05-2018
Draft Genome Sequence of the Chronic, Nonclonal Cystic Fibrosis Isolate Pseudomonas aeruginosa Strain 18A
Publisher: American Society for Microbiology
Date: 02-05-2013
Abstract: Pseudomonas aeruginosa strain 18A is a clinical, nonclonal isolate retrieved from the sputum of a chronically infected cystic fibrosis patient. The genome of 18A was sequenced for comparison with environmental and clinical isolates to identify genes that might facilitate its persistence during infection.
Kinetics of the AHL Regulatory System in a Model Biofilm System: How Many Bacteria Constitute a “Quorum”?
Publisher: Elsevier BV
Date: 06-2008
Remote control of biofouling by heating PDMS/MnZn ferrite nanocomposites with an alternating magnetic field
Publisher: Wiley
Date: 14-06-2019
DOI: 10.1002/JCTB.6083
Abstract: The accumulation of unwanted microorganisms on wetted surfaces, leading to surface damage and contamination, is a common and significant global issue. Herein, we report a novel technique where the growth of microorganisms can be readily controlled by coating the surfaces with a polydimethylsiloxane (PDMS)/Mn 0.8 Zn 0.2 Fe 2 O 4 (manganese‐zinc ferrite) nanocomposite followed by applying alternating magnetic field (AMF). The PDMS/MnZn ferrite nanocomposite is light weight and thermally stable (up to ∼ 330 °C) that can form a flexible coating. PDMS also provides hydrophobicity, which is further enhanced by the addition of Mn and Zn. The improved hydrophobicity makes the coated surface less susceptible to biofilm formation. When external AMF was applied to nanocomposites containing various MnZn ferrite nanoparticle loads of 10%, 20% and 30%, the temperature of the surface of nanocomposites reached to 80, 120 and 160 °C, respectively. Successful biofilm deactivation was achieved by heating the nanocomposites via AMF application, as shown in the biofilm test where up to ∼ 70% of the Pseudomonas aeruginosa PAO1 biofilm cells were killed when the AMF was applied for 20 min to the nanocomposites containing 30% nanoparticles. Coating the surface with PDMS/MnZn ferrite nanocomposites followed by applying external AMF can be an effective way to remove biofilm remotely in a wide range of applications. © 2019 Society of Chemical Industry
Adaptation to an amoeba host drives selection of virulence-associated traits in Vibrio cholerae
Publisher: Springer Science and Business Media LLC
Date: 15-10-2022
DOI: 10.1038/S41396-021-01134-2
Abstract: Predation by heterotrophic protists drives the emergence of adaptive traits in bacteria, and often these traits lead to altered interactions with hosts and persistence in the environment. Here we studied adaptation of the cholera pathogen, Vibrio cholerae during long-term co-incubation with the protist host, Acanthamoeba castellanii . We determined phenotypic and genotypic changes associated with long-term intra-amoebal host adaptation and how this impacts pathogen survival and fitness. We showed that adaptation to the amoeba host leads to temporal changes in multiple phenotypic traits in V. cholerae that facilitate increased survival and competitive fitness in amoeba. Genome sequencing and mutational analysis revealed that these altered lifestyles were linked to non-synonymous mutations in conserved regions of the flagellar transcriptional regulator, flrA . Additionally, the mutations resulted in enhanced colonisation in zebrafish, establishing a link between adaptation of V. cholerae to amoeba predation and enhanced environmental persistence. Our results show that pressure imposed by amoeba on V. cholerae selects for flrA mutations that serves as a key driver for adaptation. Importantly, this study provides evidence that adaptive traits that evolve in pathogens in response to environmental predatory pressure impact the colonisation of eukaryotic organisms by these pathogens.
Signal-mediated cross-talk regulates stress adaptation in Vibrio species
Publisher: Microbiology Society
Date: 07-2003
Abstract: Quorum sensing systems serve as a means of ‘census taking’ of conspecific and non-conspecific bacteria in the near vicinity. The acylated homoserine lactone (AHL) quorum sensing system has been proposed to be primarily an intra-specific communication system, while the AI-2 autoinducer signalling system is proposed to be an interspecific communication system. Here it is shown that AI-2-like signalling in two marine Vibrio species, Vibrio vulnificus and ‘ Vibrio angustum ’ S14, induces the core response phenotypes of starvation adaptation and stress resistance, and that a signal antagonist can competitively inhibit these phenotypes. Furthermore, the signals produced by a range of Vibrio species have the ability to induce these phenotypes in V. vulnificus and ‘ V. angustum ’ S14, indicating that, at least in Vibrio species, AI-2-like signalling systems function as interspecies communication systems capable of ‘cross-talk’ and of regulating environmentally relevant phenotypes.
Enhanced Shewanella biofilm promotes bioelectricity generation
Publisher: Wiley
Date: 12-05-2015
DOI: 10.1002/BIT.25624
Abstract: Electroactive biofilms play essential roles in determining the power output of microbial fuel cells (MFCs). To engineer the electroactive biofilm formation of Shewanella oneidensis MR-1, a model exoelectrogen, we herein heterologously overexpressed a c-di-GMP biosynthesis gene ydeH in S. oneidensis MR-1, constructing a mutant strain in which the expression of ydeH is under the control of IPTG-inducible promoter, and a strain in which ydeH is under the control of a constitutive promoter. Such engineered Shewanella strains had significantly enhanced biofilm formation and bioelectricity generation. The MFCs inoculated with these engineered strains accomplished a maximum power density of 167.6 ± 3.6 mW/m(2) , which was ∼ 2.8 times of that achieved by the wild-type MR-1 (61.0 ± 1.9 mW/m(2) ). In addition, the engineered strains in the bioelectrochemical system at poised potential of 0.2 V vs. saturated calomel electrode (SCE) generated a stable current density of 1100 mA/m(2) , ∼ 3.4 times of that by wild-type MR-1 (320 mA/m(2) ).
Quorum-Sensing Regulation of Adhesion in Serratia marcescens MG1 Is Surface Dependent
Publisher: American Society for Microbiology
Date: 04-2007
DOI: 10.1128/JB.01582-06
Abstract: Serratia marcescens is an opportunistic pathogen and a major cause of ocular infections. In previous studies of S. marcescens MG1, we showed that biofilm maturation and sloughing were regulated by N -acyl homoserine lactone (AHL)-based quorum sensing (QS). Because of the importance of adhesion in initiating biofilm formation and infection, the primary goal of this study was to determine whether QS is important in adhesion to both abiotic and biotic surfaces, as assessed by determining the degree of attachment to hydrophilic tissue culture plates and human corneal epithelial (HCE) cells. Our results demonstrate that while adhesion to the abiotic surface was AHL regulated, adhesion to the HCE cell biotic surface was not. Type I fimbriae were identified as the critical adhesin for non-QS-mediated attachment to the biotic HCE cell surface but played no role in adhesion to the abiotic surface. While we were not able to identify a single QS-regulated adhesin essential for attachment to the abiotic surface, four AHL-regulated genes involved in adhesion to the abiotic surface were identified. Interestingly, two of these genes, bsmA and bsmB , were also shown to be involved in adhesion to the biotic surface in a non-QS-controlled fashion. Therefore, the expression of these two genes appears to be cocontrolled by regulators other than the QS system for mediation of attachment to HCE cells. We also found that QS in S. marcescens regulates other potential cell surface adhesins, including exopolysaccharide and the outer membrane protein OmpX. We concluded that S. marcescens MG1 utilizes different regulatory systems and adhesins in attachment to biotic and abiotic surfaces and that QS is a main regulatory pathway in adhesion to an abiotic surface but not in adhesion to a biotic surface.
SiaA/D Interconnects c-di-GMP and RsmA Signaling to Coordinate Cellular Aggregation of Pseudomonas aeruginosa in Response to Environmental Conditions
Publisher: Frontiers Media SA
Date: 26-02-2016
Associational Resistance to Predation by Protists in a Mixed Species Biofilm
Publisher: American Society for Microbiology
Date: 28-02-2023
DOI: 10.1128/AEM.01741-22
Abstract: Biofilms have been shown to protect bacterial cells from predation by protists. Biofilm studies have traditionally used single species systems, which have provided information on the mechanisms and regulation of biofilm formation and dispersal, and the effects of predation on these biofilms.
Interspecies interactions in bacterial colonies are determined by physiological traits and the environment
Publisher: Cold Spring Harbor Laboratory
Date: 30-04-2019
DOI: 10.1101/623017
Abstract: Interspecies interactions in bacterial biofilms have important impacts on the composition and function of communities in natural and engineered systems. To investigate these interactions, synthetic communities provide experimentally tractable systems. Agar-surface colonies are similar to biofilms and have been used for investigating the eco-evolutionary and biophysical forces that determine community composition and spatial distribution of bacteria. Prior work has focused on intraspecies interactions, using differently fluorescent tagged but identical or genetically modified strains of the same species. Here, we investigated how physiological differences determine the community composition and spatial distribution in synthetic communities of Pseudomonas aeruginosa , Pseudomonas protegens and Klebsiella pneumoniae . Using quantitative microscopic imaging, we found that interspecies interactions in multispecies colonies are influenced by type IV pilus mediated motility, extracellular matrix secretion, environmental parameters and the specific species involved. These results indicate that the patterns observable in mixed species colonies can be used to understand the mechanisms that drive interspecies interactions, which are dependent on the interplay between specific species’ physiology and environmental conditions.
Nanoparticles of Short Cationic Peptidopolysaccharide Self-Assembled by Hydrogen Bonding with Antibacterial Effect against Multidrug-Resistant Bacteria
Publisher: American Chemical Society (ACS)
Date: 13-10-2017
Abstract: Cationic antimicrobial peptides (AMPs) and polymers are active against many multidrug-resistant (MDR) bacteria, but only a limited number of these compounds are in clinical use due to their unselective toxicity. The typical strategy for achieving selective antibacterial efficacy with low mammalian cell toxicity is through balancing the ratio of cationicity to hydrophobicity. Herein, we report a cationic nanoparticle self-assembled from chitosan-graft-oligolysine (CSM5-K5) chains with ultralow molecular weight (1450 Da) that selectively kills bacteria. Further, hydrogen bonding rather than the typical hydrophobic interaction causes the polymer chains to be aggregated together in water into small nanoparticles (with about 37 nm hydrodynamic radius) to concentrate the cationic charge of the lysine. When complexed with bacterial membrane, these cationic nanoparticles synergistically cluster anionic membrane lipids and produce a greater membrane perturbation and antibacterial effect than would be achievable by the same quantity of charge if dispersed in in idual copolymer molecules in solution. The small zeta potential (+15 mV) and lack of hydrophobicity of the nanoparticles impedes the insertion of the copolymer into the cell bilayer to improve biocompatibility. In vivo study (using a murine excisional wound model) shows that CSM5-K5 suppresses the growth of methicillin-resistant Staphylococcus aureus (MRSA) bacteria by 4.0 orders of magnitude, an efficacy comparable to that of the last resort MRSA antibiotic vancomycin it is also noninflammatory with little/no activation of neutrophils (CD11b and Ly6G immune cells). This study demonstrates a promising new class of cationic polymers-short cationic peptidopolysaccharides-that effectively attack MDR bacteria due to the synergistic clustering of, rather than insertion into, bacterial anionic lipids by the concentrated polymers in the resulting hydrogen-bonding-stabilized cationic nanoparticles.
Bacterial Reverse Transcriptase and msDNA
Publisher: Springer US
Date: 1996
Nitric Oxide-Mediated Induction of Dispersal in Pseudomonas aeruginosa Biofilms Is Inhibited by Flavohemoglobin Production and Is Enhanced by Imidazole
Publisher: American Society for Microbiology
Date: 03-2018
DOI: 10.1128/AAC.01832-17
Abstract: The biological signal molecule nitric oxide (NO) was found to induce biofilm dispersal across a range of bacterial species, which led to its consideration for therapeutic strategies to treat biofilms and biofilm-related infections. However, biofilms are often not completely dispersed after exposure to NO. To better understand this phenomenon, we investigated the response of Pseudomonas aeruginosa biofilm cells to successive NO treatments. When biofilms were first pretreated with a low, noneffective dose of NO, a second dose of the signal molecule at a concentration usually capable of inducing dispersal did not have any effect. Amperometric analysis revealed that pretreated P. aeruginosa cells had enhanced NO-scavenging activity, and this effect was associated with the production of the flavohemoglobin Fhp. Further, quantitative real-time reverse transcription-PCR (qRT-PCR) analysis showed that fhp expression increased by over 100-fold in NO-pretreated biofilms compared to untreated biofilms. Biofilms of mutant strains harboring mutations in fhp or fhpR , encoding a NO-responsive regulator of fhp , were not affected in their dispersal response after the initial pretreatment with NO. Overall, these results suggest that FhpR can sense NO to trigger production of the flavohemoglobin Fhp and inhibit subsequent dispersal responses to NO. Finally, the addition of imidazole, which can inhibit the NO dioxygenase activity of flavohemoglobin, attenuated the prevention of dispersal after NO pretreatment and improved the dispersal response in older, starved biofilms. This study clarifies the underlying mechanisms of impaired dispersal induced by repeated NO treatments and offers a new perspective for improving the use of NO in biofilm control strategies.
Microbial biofilms are shaped by the constant dialogue between biological and physical forces in the extracellular matrix
Publisher: Wiley
Date: 23-12-2022
The genomic basis of trophic strategy in marine bacteria
Publisher: Proceedings of the National Academy of Sciences
Date: 15-09-2009
Abstract: Many marine bacteria have evolved to grow optimally at either high (copiotrophic) or low (oligotrophic) nutrient concentrations, enabling different species to colonize distinct trophic habitats in the oceans. Here, we compare the genome sequences of two bacteria, Photobacterium angustum S14 and Sphingopyxis alaskensis RB2256, that serve as useful model organisms for copiotrophic and oligotrophic modes of life and specifically relate the genomic features to trophic strategy for these organisms and define their molecular mechanisms of adaptation. We developed a model for predicting trophic lifestyle from genome sequence data and tested ,000 proteins representing million nucleotides of sequence data from 126 genome sequences with metagenome data of whole environmental s les. When applied to available oceanic metagenome data (e.g., the Global Ocean Survey data) the model demonstrated that oligotrophs, and not the more readily isolatable copiotrophs, dominate the ocean's free-living microbial populations. Using our model, it is now possible to define the types of bacteria that specific ocean niches are capable of sustaining.
Vibrio vulnificus: a physiological and genetic approach to the viable but nonculturable response.
Publisher: Elsevier BV
Date: 2000
DOI: 10.1007/PL00012150
Cyclic-di-GMP is required for corneal infection byPseudomonas aeruginosaand modulates host immunity
Publisher: Cold Spring Harbor Laboratory
Date: 06-01-2017
DOI: 10.1101/098749
Abstract: Biofilms are extremely tolerant toward antimicrobial treatment and host immune clearance due to their distinct physiology and protection by extracellular polymeric substances. Bis-(3´-5´)-cyclic dimeric guanosine monophosphate (c-di-GMP) is an essential messenger that regulates biofilm formation by a wide range of bacteria. However, there is a lack of physiological characterization of biofilms in vivo as well as the roles of c-di-GMP signaling in mediating host-biofilm interactions. Here, we employed dual RNA-Seq to characterize the host and pathogen transcriptomes during Pseudomonas aeruginosa infection using a mouse keratitis model. In vivo P. aeruginosa biofilms maintained a distinct physiology compared with in vitro P. aeruginosa biofilms, with enhanced virulence and iron uptake capacity. C-di-GMP synthesis was enhanced in P. aeruginosa cells in vivo, potentially due to down-regulation of the expression of several phosphodiesterases (e.g., DipA, NbdA). Increased intracellular c-di-GMP levels were required for long-term ocular colonization of P. aeruginosa and impaired host innate immunity.
Detection and inhibition of bacterial cell-cell communication
Publisher: Humana Press
Date: 2007
DOI: 10.1007/978-1-60327-032-8_5
Abstract: Bacteria communicate with other members of their community through the secretion and perception of small chemical cues or signals. The recognition of a signal normally leads to the expression of a large suite of genes, which in some bacteria are involved in the regulation of virulence factors, and as a result, these signaling compounds are key regulatory factors in many disease processes. Thus, it is of interest when studying pathogens to understand the mechanisms used to control the expression of virulence genes so that strategies might be devised for the control of those pathogens. Clearly, the ability to interfere with this process of signaling represents a novel approach for the treatment of bacterial infections. There is a broad range of compounds that bacteria can use for signaling purposes, including fatty acids, peptides, N-acylated homoserine lactones, and the signals collectively called autoinducer 2 (AI-2). This chapter will focus on the latter two signaling systems as they are present in a range of medically relevant bacteria, and here we describe assays for determining whether an organism produces a particular signal and assays that can be used to identify inhibitors of the signaling cascade. Lastly, the signal detection and inhibition assays will be directly linked to the expression of virulence factors of specific pathogens.
Acoustically stressing biofilms formed by Pseudomonas aeruginosa
Publisher: Acoustical Society of America (ASA)
Date: 10-2019
DOI: 10.1121/1.5137506
Abstract: Bacterial biofilms, the complex and dynamic assemblages of bacterial cells, have shown increased tolerance to antimicrobials compared to their planktonic counterparts. Altered metabolism and micro-environments, in addition to the self-generated extracellular polymeric substances (EPS), collectively help to protect the bacteria from the effect of antimicrobials, thereby increasing the necessity for novel treatment methods that are effective against biofilms. To address this, we have investigated the effect of high intensity focused ultrasound (HIFU) in killing or dispersing biofilms. HIFU reduces the total biofilm biomass without significant cell killing. To investigate the molecular mechanism of action of HIFU, we quantified the intracellular concentrations of cyclic di-GMP, which regulates the switch between biofilm and planktonic life-styles. Biofilms grown on polymeric sheets were exposed to HIFU at 0.5 MHz frequency and the c di-GMP concentration was characterized using confocal microscopy. Changes in the c di-GMP activity localized at the acoustic focus were observed as the biomass decreased. The mechanisms promoting these changes were further investigated by examining the shape of in idual bacterial colony grown on agar plates. The observed effects were compared to sham (negative control) and c di-GMP overproducing mutant (positive control).
ELECTRONIC EXCITED STATES OF LIQUIDS
Publisher: Acoustical Society of America (ASA)
Date: 1969
DOI: 10.1121/1.1971300
Abstract: This talk will deal with the study of the electronic excited states of liquids. Our purpose is twofold: (1) to describe these states and understand how electronic excitation may propagate through a disordered system (2) to understand how molecular motion alters the properties of electronic excited states. It will be shown that, in principle, a study of the electronic excited states of a liquid can lead to useful information concerning the collective translational excitations of the ground electronic state of a liquid.
Interspecific diversity reduces and functionally substitutes for intraspecific variation in biofilm communities
Publisher: Springer Science and Business Media LLC
Date: 25-09-2015
Bacteriophage evolution drives Pseudomonas aeruginosa PAO1 biofilm diversification
Publisher: Springer Science and Business Media LLC
Date: 21-11-2011
Machine-learning based detection of adventitious microbes in T-cell therapy cultures using long read sequencing
Publisher: Cold Spring Harbor Laboratory
Date: 04-11-2022
DOI: 10.1101/2022.11.03.514634
Abstract: Assuring that cell therapy products are safe before releasing them for use in patients is critical. Currently, compendial sterility testing for bacteria and fungi can take 7-14 days. The goal of this work was to develop a rapid untargeted approach for the sensitive detection of microbial contaminants at low abundance from low volume s les during the manufacturing process of cell therapies. We developed a long-read sequencing methodology using Oxford Nanopore Technologies MinION platform with 16S and 18S licon sequencing to detect USP organisms and other microbial species. Reads are classified metagenomically to predict the microbial species. We used an extreme gradient boosting machine learning algorithm (XGBoost) to first assess if a s le is contaminated and second, determine whether the predicted contaminant is correctly classified or misclassified. The model was used to make a final decision on the sterility status of the input s le. An optimised experimental and bioinformatics pipeline starting from spiked species through to sequenced reads allowed for the detection of microbial s les at 10 CFU / mL using metagenomic classification. Machine learning can be coupled with long read sequencing to detect and identify s le sterility status and microbial species present in T-cell cultures, including the USP organisms to 10 CFU / mL. This research presents a novel method for rapidly and accurately detecting microbial contaminants in cell therapy products, which is essential for ensuring patient safety. Traditional testing methods are time-consuming, taking 7-14 days, while our approach can significantly reduce this time. By combining advanced long read Nanopore sequencing techniques and machine learning, we can effectively identify the presence and types of microbial contaminants at low abundance levels. This breakthrough has the potential to improve the safety and efficiency of cell therapy manufacturing, leading to better patient outcomes and a more streamlined production process.
Development of a quorum quenching-column to control biofouling in reverse osmosis water treatment processes
Publisher: Elsevier BV
Date: 02-2021
Evolution of biofilm-forming pathogenic bacteria in the presence of nanoparticles and antibiotic: adaptation phenomena and cross-resistance
Publisher: Springer Science and Business Media LLC
Date: 27-09-2021
DOI: 10.1186/S12951-021-01027-8
Abstract: Treatment of bacterial biofilms are difficult and in many cases, expensive. Bacterial biofilms are naturally more resilient to antimicrobial agents than their free-living planktonic counterparts, rendering the community growth harder to control. The present work described the risks of long-term use of an important alternative antimicrobial, silver nanoparticles (NAg), for the first time, on the dominant mode of bacterial growth. NAg could inhibit the formation as well as eradicating an already grown biofilm of Pseudomonas aeruginosa , a pathogen notorious for its resilience to antibiotics. The biofilm-forming bacterium however, evolved a reduced sensitivity to the nanoparticle. Evidence suggests that survival is linked to the development of persister cells within the population. A similar adaptation was also seen upon prolonged exposures to ionic silver (Ag + ). The persister population resumed normal growth after subsequent passage in the absence of silver, highlighting the potential risks of recurrent infections with long-term NAg (and Ag + ) treatments of biofilm growth. The present study further observed a potential silver/antibiotic cross-resistance, whereby NAg (as well as Ag + ) could not eradicate an already growing gentamicin-resistant P. aeruginosa biofilm. The phenomena is thought to result from the hindered biofilm penetration of the silver species. In contrast, both silver formulations inhibited biofilm formation of the resistant strain, presenting a promising avenue for the control of biofilm-forming antibiotic-resistant bacteria. The findings signify the importance to study the nanoparticle adaptation phenomena in the biofilm mode of bacterial growth, which are apparently unique to those already reported with the planktonic growth counterparts. This work sets the foundation for future studies in other globally significant bacterial pathogens when present as biofilms. Scientifically based strategies for management of pathogenic growth is necessary, particularly in this era of increasing antibiotic resistance.
The marine pathogen Vibrio vulnificus encodes a putative homologue of the Vibrio harveyi regulatory gene, luxR: A genetic and phylogenetic comparison
Publisher: Elsevier BV
Date: 05-2000
DOI: 10.1016/S0378-1119(00)00117-7
Abstract: Vibrio vulnificus is an opportunistic pathogen that exhibits numerous virulence factors, including the secretion of a zinc metalloprotease and the production of a capsule. We have cloned and sequenced a gene from V. vulnificus that is a homologue of the positive transcriptional regulator, luxR, of the lux operon in Vibrio harveyi. This gene encodes a putative, single complete open reading frame designated smcR, which shares greater than 75% nucleotide identity with luxR of V. harveyi. The deduced amino acid sequence of the putative SmcR protein is more than 90% identical and 95% similar to that of LuxR of V. harveyi, suggesting that V. vulnificus possesses a member of the family of signal-response genes recently described in Vibrio cholerae and in Vibrio parahaemolyticus. Our data also demonstrate that, in addition to V. vulnificus, all six Vibrio spp. tested contained genes that hybridized with the luxR probe. We also present evidence that this regulatory protein was inherited from a common ancestor, and that the gene is ancient and widespread in marine Vibrio spp.
Committee on government statistics and information services
Publisher: Informa UK Limited
Date: 09-1933
Isolation of Bdellovibrio bacteriovorus from a tropical wastewater treatment plant and predation of mixed species biofilms assembled by the native community members
Publisher: Wiley
Date: 08-07-2016
Abstract: It is reported here that a predatory bacterium belonging to the Genus Bdellovibrio, was isolated from activated sludge at the Ulu Pandan Water Reclamation Plant, Singapore. 16S rDNA gene sequencing analysis revealed that this isolate was 99% identical to 'Bdellovibrio bacteriovorus strain Tiberius' and hence is designated as 'Bdellovibrio bacteriovorus UP'. Using a novel approach based on fluorescence in situ hybridization (FISH), a prey cell density-dependent growth pattern of B. bacteriovorus UP was established. B. bacteriovorus UP preyed upon a broad range of bacterial species (60 species) isolated from the activated sludge. Except for Ochrobactrum anthropi, all Gram-negative species were sensitive to predation by B. bacteriovorus UP irrespective of the mode of growth (planktonic or biofilm). Similarly, the predation-sensitive species were not protected by the predation-resistant species, O. anthropi, as determined in multiple dual-species planktonic and biofilm consortia. Given the broad prey spectrum, B. bacteriovorus UP may impact functional community members, which are largely members of the Proteobacteria. Thus, these results provide an important insight to the role of predatory bacteria in shaping of community structure and function in both natural and engineered ecosystems.
Probing the internal micromechanical properties of Pseudomonas aeruginosa biofilms by Brillouin imaging
Publisher: Springer Science and Business Media LLC
Date: 08-09-2017
DOI: 10.1038/S41522-017-0028-Z
Abstract: Biofilms are organised aggregates of bacteria that adhere to each other or surfaces. The matrix of extracellular polymeric substances that holds the cells together provides the mechanical stability of the biofilm. In this study, we have applied Brillouin microscopy, a technique that is capable of measuring mechanical properties of specimens on a micrometre scale based on the shift in frequency of light incident upon a s le due to thermal fluctuations, to investigate the micromechanical properties of an active, live Pseudomonas aeruginosa biofilm. Using this non-contact and label-free technique, we have extracted information about the internal stiffness of biofilms under continuous flow. No correlation with colony size was found when comparing the averages of Brillouin shifts of two-dimensional cross-sections of randomly selected colonies. However, when focusing on single colonies, we observed two distinct spatial patterns: in smaller colonies, stiffness increased towards their interior, indicating a more compact structure of the centre of the colony, whereas, larger (over 45 μm) colonies were found to have less stiff interiors.
Modulating Antimicrobial Activity and Mammalian Cell Biocompatibility with Glucosamine-Functionalized Star Polymers
Publisher: American Chemical Society (ACS)
Date: 09-02-2016
DOI: 10.1021/ACS.BIOMAC.5B01766
Abstract: The development of novel reagents and antibiotics for combating multidrug resistance bacteria has received significant attention in recent years. In this study, new antimicrobial star polymers (14-26 nm in diameter) that consist of mixtures of polylysine and glycopolymer arms were developed and were shown to possess antimicrobial efficacy toward Gram positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) (with MIC values as low as 16 μg mL(-1)) while being non-hemolytic (HC50 > 10,000 μg mL(-1)) and exhibit excellent mammalian cell biocompatibility. Structure function analysis indicated that the antimicrobial activity and mammalian cell biocompatibility of the star nanoparticles could be optimized by modifying the molar ratio of polylysine to glycopolymers arms. The technology described herein thus represents an innovative approach that could be used to fight deadly infectious diseases.
Defences against oxidative stress during starvation in bacteria
Publisher: Springer Science and Business Media LLC
Date: 2002
Abstract: It now seems clear that starvation adaptation is important for cells to initiate long-term survival under conditions of not only nutrient depletion but to develop resistance to other stresses, most notably oxidative stress. Clearly, oxidative stress is a condition likely to be perceived by many bacteria, for ex le, in the form of reactive oxygen species derived from metabolic processes or from near-UV exposure. We have found evidence for a large degree of overlap in the cell's use of global regulators to deal with both starvation and oxidative stress. Both SpoT and AI-2 signalling pathways are important regulators of starvation and stress adaptation as well as the alternative sigma factor, RpoE. We also present evidence that suggests that AI-2 signalling can mediate starvation adaptation at the molecular level by increasing the stability of the mRNAs so that cells are prepared for rapid response to nutrient addition. Moreover, such extracellular signals mediate intraspecies communication to enable enhanced survival and stress resistance of neighbouring bacterial cells. It is likely that bacteria rely on a suite of effects between cells and on transcription, translation and post-translationalprocesses, mediated by global regulators and signalling molecules, to meet their needs for growth and survival.
Loss of the Acetate Switch in Vibrio vulnificus Enhances Predation Defense against Tetrahymena pyriformis
Publisher: American Society for Microbiology
Date: 25-01-2022
DOI: 10.1128/AEM.01665-21
Abstract: Bacteria in the environment, including Vibrio spp., interact with protozoan predators. To defend against predation, bacteria evolve antipredator mechanisms ranging from changing morphology, biofilm formation, and secretion of toxins or virulence factors.
Biofouling control in reverse osmosis by nitric oxide treatment and its impact on the bacterial community
Publisher: Elsevier BV
Date: 03-2018
Biological limits in the development of society
Publisher: Oxford University Press (OUP)
Date: 04-1924
Hybrids of acylated homoserine lactone and nitric oxide donors as inhibitors of quorum sensing and virulence factors in Pseudomonas aeruginosa
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5OB01373A
Abstract: This paper discusses conversion of agonist acylated homoserine lactones (AHL) to antagonist AHLs with dual properties of quorum sensing inhibition and nitric oxide release.
Urinary catheter-associated microbiota change in accordance with treatment and infection status
Publisher: Public Library of Science (PLoS)
Date: 19-06-2017
Nitrite production by ammonia‐oxidizing bacteria mediates chloramine decay and resistance in a mixed‐species community
Publisher: Wiley
Date: 30-07-2020
Accessory genome of the multi-drug resistant ocular isolate of Pseudomonas aeruginosa PA34
Publisher: Public Library of Science (PLoS)
Date: 15-04-2019
Mechanical properties of the superficial biofilm layer determine the architecture of biofilms
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6SM00687F
Abstract: Cells in biofilms sense and interact with their environment through the extracellular matrix. The physicochemical properties of the matrix, particularly at the biofilm-environment interface, determine how cells respond to changing conditions. In this study we describe the application of atomic force microscopy and confocal imaging to probe in situ the mechanical properties of these interfacial regions and to elucidate how key matrix components can contribute to the physical sensing by the cells. We describe how the Young's modulus of microcolonies differs according to the size and morphology of microcolonies, as well as the flow rate. The Young's modulus increased as a function of microcolony diameter, which was correlated with the production of the polysaccharide Psl at later stages of maturation for hemispherical or mushroom shaped microcolonies. The Young's modulus of the periphery of the biofilm colony was however independent of the hydrodynamic shear. The morphology of the microcolonies also influenced interfacial or peripheral stiffness. Microcolonies with a diffuse morphology had a lower Young's modulus than isolated, circular ones and this phenomenon was due to a deficiency of Psl. In this way, changes in the specific polysaccharide components imbue the biofilm with distinct physical properties that may modulate the way in which bacteria perceive or respond to their environment. Further, the physical properties of the polysaccharides are closely linked to the specific architectures formed by the developing biofilm.
Microbial predation accelerates granulation and modulates microbial community composition
Publisher: Springer Science and Business Media LLC
Date: 27-03-2021
DOI: 10.1186/S12866-021-02156-8
Abstract: Bacterial communities are responsible for biological nutrient removal and flocculation in engineered systems such as activated floccular sludge. Predators such as bacteriophage and protozoa exert significant predation pressure and cause bacterial mortality within these communities. However, the roles of bacteriophage and protozoan predation in impacting granulation process remain limited. Recent studies hypothesised that protozoa, particularly sessile ciliates, could have an important role in granulation as these ciliates were often observed in high abundance on surfaces of granules. Bacteriophages were hypothesized to contribute to granular stability through bacteriophage-mediated extracellular DNA release by lysing bacterial cells. This current study investigated the bacteriophage and protozoan communities throughout the granulation process. In addition, the importance of protozoan predation during granulation was also determined through chemical killing of protozoa in the floccular sludge. Four independent bioreactors seeded with activated floccular sludge were operated for aerobic granulation for 11 weeks. Changes in the phage, protozoa and bacterial communities were characterized throughout the granulation process. The filamentous phage, Inoviridae, increased in abundance at the initiation phase of granulation. However, the abundance shifted towards lytic phages during the maturation phase. In contrast, the abundance and ersity of protozoa decreased initially, possibly due to the reduction in settling time and subsequent washout. Upon the formation of granules, ciliated protozoa from the class Oligohymenophorea were the dominant group of protozoa based on metacommunity analysis. These protozoa had a strong, positive-correlation with the initial formation of compact aggregates prior to granule development. Furthermore, chemical inhibition of these ciliates in the floccular sludge delayed the initiation of granule formation. Analysis of the bacterial communities in the thiram treated sludge demonstrated that the recovery of ‘ Candidatus Accumulibacter’ was positively correlated with the formation of compact aggregates and granules. Predation by bacteriophage and protozoa were positively correlated with the formation of aerobic granules. Increases in Inoviridae abundance suggested that filamentous phages may promote the structural formation of granules. Initiation of granules formation was delayed due to an absence of protozoa after chemical treatment. The presence of ‘ Candidatus Accumulibacter’ was necessary for the formation of granules in the absence of protozoa.
Insights into Biofilm Dispersal Regulation from the Crystal Structure of the PAS-GGDEF-EAL Region of RbdA from Pseudomonas aeruginosa
Publisher: American Society for Microbiology
Date: 02-2018
DOI: 10.1128/JB.00515-17
Abstract: RbdA is a positive r egulator of b iofilm d ispersal of Pseudomonas aeruginosa . Its cytoplasmic region (cRbdA) comprises an N-terminal Per-ARNT-Sim (PAS) domain followed by a diguanylate cyclase (GGDEF) domain and an EAL domain, whose phosphodiesterase activity is allosterically stimulated by GTP binding to the GGDEF domain. We report crystal structures of cRbdA and of two binary complexes: one with GTP/Mg 2+ bound to the GGDEF active site and one with the EAL domain bound to the c-di-GMP substrate. These structures unveil a 2-fold symmetric dimer stabilized by a closely packed N-terminal PAS domain and a noncanonical EAL dimer. The autoinhibitory switch is formed by an α-helix (S-helix) immediately N-terminal to the GGDEF domain that interacts with the EAL dimerization helix (α 6-E ) of the other EAL monomer and maintains the protein in a locked conformation. We propose that local conformational changes in cRbdA upon GTP binding lead to a structure with the PAS domain and S-helix shifted away from the GGDEF-EAL domains, as suggested by small-angle X-ray scattering (SAXS) experiments. Domain reorientation should be facilitated by the presence of an α-helical lever (H-helix) that tethers the GGDEF and EAL regions, allowing the EAL domain to rearrange into an active dimeric conformation. IMPORTANCE Biofilm formation by bacterial pathogens increases resistance to antibiotics. RbdA positively regulates biofilm dispersal of Pseudomonas aeruginosa . The crystal structures of the cytoplasmic region of the RbdA protein presented here reveal that two evolutionarily conserved helices play an important role in regulating the activity of RbdA, with implications for other GGDEF-EAL dual domains that are abundant in the proteomes of several bacterial pathogens. Thus, this work may assist in the development of small molecules that promote bacterial biofilm dispersal.
Microbial activity in biofilter used as a pretreatment for seawater desalination
Publisher: Elsevier BV
Date: 2013
Inhibition of quorum sensing in Pseudomonas aeruginosa biofilm bacteria by a halogenated furanone compound
Publisher: Microbiology Society
Date: 2002
DOI: 10.1099/00221287-148-1-87
Abstract: Novel molecular tools have been constructed which allow for in situ detection of N-acyl homoserine lactone (AHL)-mediated quorum sensing in Pseudomonas aeruginosa biofilms. The reporter responds to AHL activation of LasR by expression of an unstable version of the green-fluorescent protein (Gfp). Gfp-based reporter technology has been applied for non-destructive, single-cell-level detection of quorum sensing in laboratory-based P. aeruginosa biofilms. It is reported that a synthetic halogenated furanone compound, which is a derivative of the secondary metabolites produced by the Australian macroalga Delisea pulchra, is capable of interfering with AHL-mediated quorum sensing in P. aeruginosa. It is demonstrated that the furanone compound specifically represses expression of a PlasB-gfp reporter fusion without affecting growth or protein synthesis. In addition, it reduces the production of important virulence factors, indicating a general effect on target genes of the las quorum sensing circuit. The furanone was applied to P. aeruginosa biofilms established in biofilm flow chambers. The Gfp-based analysis reveals that the compound penetrates microcolonies and blocks cell signalling and quorum sensing in most biofilm cells. The compound did not affect initial attachment to the abiotic substratum. It does, however, affect the architecture of the biofilm and enhances the process of bacterial detachment, leading to a loss of bacterial biomass from the substratum.
Environmental cues and genes involved in establishment of the superinfective Pf4 phage of Pseudomonas aeruginosa
Publisher: Frontiers Media SA
Date: 02-12-2014
The biofilm life cycle and virulence of Pseudomonas aeruginosa are dependent on a filamentous prophage
Publisher: Springer Science and Business Media LLC
Date: 13-11-2008
Strain-specific parallel evolution drives short-term diversification during Pseudomonas aeruginosa biofilm formation.
Publisher: Proceedings of the National Academy of Sciences
Date: 28-03-2014
Abstract: Within-population genetic ersity is an essential evolutionary prerequisite for processes ranging from antibiotic resistance to niche adaptation, but its generation is poorly understood, with most studies focusing on fixed substitutions at the end point of long-term evolution. Using deep sequencing, we analyzed short-term, within-population genetic ersification occurring during biofilm formation of the model bacterium Pseudomonas aeruginosa . We discovered extensive parallel evolution between biological replicates at the level of pathways, genes, and even in idual nucleotides. Short-term ersification featured positive selection of relatively few nonsynonymous mutations, with the majority of the genome being conserved by negative selection. This result is broadly consistent with observations of long-term evolution and suggests ersifying selection may underlie genetic ersification of Pseudomonas aeruginosa biofilms.
Bacterial communication: when does a metabolite become a signal?
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/MA06115
Abstract: Bacterial communication has risen to prominence in microbiology as a dynamic research topic, both because of its role in microbial ecology and evolution and for the opportunity it offers to control pathogenic microbial activity. Bacterial communication has evolved from the metabolic processes of prokaryotic cellular life, in which the biosynthesis and breakdown of chemical compounds in central metabolism generates secondary metabolites with ambiguous utility in natural selection.
Fluroxene mutagenicity.
Publisher: Elsevier BV
Date: 11-1978
DOI: 10.1016/0165-1218(78)90008-3
Abstract: The commercially available volatile anesthetic fluroxene (2,2,2-trifluoroethyl vinyl ether) which contains the stabilizer N-phenyl-1-napthylamine, was tested for mutagenicity using four strains of S. typhimurium, TA1535, TA1537, TA98 and TA100, and one strain of E. coli, WP2. In addition, purified fluroxene N-phenyl-1-napthylamine trifluoroethanol, a major metabolite of fluoroxene and urine from rats anesthetized with fluroxene were tested. Several procedures were utilized including exposure of bacteria to vapor in desiccators and in liquid suspension. Results indicate that fluroxene, but not its stabilizer, was mutagenic to strains TA1535, TA100 and WP2 only in liquid suspension and only in the presence of a rat-liver enzyme system. Trifluoroethanol and urine from fluroxene-treated rat were not mutagenic to any strain of bacteria. These findings indicate that fluroxene is a promutagen which requires preincubation before it is recognized. Further experiments were performed with enzymes prepared from mouse, hamster and human liver. Fluroxene was mutagenic only in the presence of enzymes prepared from Aroclor 1254 pretreated rodents. Since fluroxene was not mutagenic in the presence of enzymes prepared from three human livers, the significance of these findings to man are unclear.
Biofouling in reverse osmosis processes: The roles of flux, crossflow velocity and concentration polarization in biofilm development
Publisher: Elsevier BV
Date: 10-2014
Optimal dosing regimen of nitric oxide donor compounds for the reduction ofPseudomonas aeruginosabiofilm and isolates from wastewater membranes
Publisher: Informa UK Limited
Date: 31-01-2013
DOI: 10.1080/08927014.2012.760069
Abstract: Membrane fouling by bacterial biofilms remains a key challenge for membrane-based water purification systems. Here, the optimal biofilm dispersal potential of three nitric oxide (NO) donor compounds, viz. sodium nitroprusside, 6-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine (MAHMA NONOate) and 1-(hydroxy-NNO-azoxy)-L-proline, disodium salt, was investigated using Pseudomonas aeruginosa PAO1 as a model organism. Dispersal was quantitatively assessed by confocal microscopy [bacterial cells and the components of the extracellular polymeric substances (EPS) (polysaccharides and extracellular DNA)] and colony-forming unit counts. The three NO donor compounds had different optimal exposure times and concentrations, with MAHMA NONOate being the optimal NO donor compound. Biofilm dispersal correlated with a reduction in both bacterial cells and EPS. MAHMA NONOate also reduced single species biofilms formed by bacteria isolated from industrial membrane bioreactor and reverse osmosis membranes, as well as in isolates combined to generate mixed species biofilms. The data present strong evidence for the application of these NO donor compounds for prevention of biofouling in an industrial setting.
AUSTIN,WILLIAM,LANE (1871-1949) - JAMES,CLYDE (1888-1949)
Publisher: Informa UK Limited
Date: 12-1949
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