ORCID Profile
0000-0003-2770-852X
Current Organisation
University of Queensland
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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)
Food Processing | Microbiology | Food Sciences not elsewhere classified | Food Sciences | Bacteriology | Microbial Genetics | Genomics | Biochemistry and Cell Biology | Cell Metabolism | Food Engineering | Food Nutritional Balance | Microbial Genetics | Signal Transduction |
ANZSRC Socio-Economic Objective (SEO)
Cheese | Expanding Knowledge in the Biological Sciences | Nutrition | Processed Milk and Cream (incl. Powder, Evaporated and Condensed) | Digestive system and disorders | Whey | Organic Industrial Chemicals (excl. Resins, Rubber and Plastics) | Dairy products | Biological sciences | Processed Food Products and Beverages (excl. Dairy Products) not elsewhere classified | Expanding Knowledge in Technology
Related Links
Publications
Review of the effects of different processing technologies on cooked and convenience rice quality
Publisher: Elsevier BV
Date: 2017
Sustained Simultaneous Delivery of Metronidazole and Doxycycline From Polycaprolactone Matrices Designed for Intravaginal Treatment of Pelvic Inflammatory Disease
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.XPHS.2017.09.033
Abstract: Poly(ɛ-caprolactone) (PCL) intravaginal matrices were produced for local delivery of a combination of antibacterials, by rapidly cooling a mixture of drug powders dispersed in PCL solution. Matrices loaded with different combinations of metronidazole (10%, 15%, and 20% w/w) and doxycycline (10% w/w) were evaluated in vitro for release behavior and antibacterial activity. Rapid "burst release" of 8%-15% of the doxycycline content and 31%-37% of the metronidazole content occurred within 24 h when matrices were immersed in simulated vaginal fluid at 37°C. The remaining drug was extracted gradually over 14 days to a maximum of 65%-73% for doxycycline and 62%-71% for metronidazole. High levels of antibacterial activity up to 89%-91% against Gardnerella vaginalis and 84%-92% against Neisseria gonorrhoeae were recorded in vitro for release media collected on day 14, compared to "nonformulated" metronidazole and doxycycline solutions. Based on the in vitro data, the minimum levels of doxycycline and metronidazole released from PCL matrices in the form of intravaginal rings into vaginal fluid in vivo were predicted to exceed the minimum inhibitory concentrations for N. gonorrhea (reported range 0.5-4.0 μg/mL) and G. vaginalis (reported range 2-12.8 μg/mL) respectively, which are 2 of the major causative agents for pelvic inflammatory disease.
Cystine uptake prevents production of hydrogen peroxide byLactobacillus fermentumBR11
Publisher: Oxford University Press (OUP)
Date: 10-2003
Salicylic acid enhances biocontrol efficacy of Rhodotorula glutinis against postharvest Rhizopus rot of strawberries and the possible mechanisms involved
Publisher: Elsevier BV
Date: 10-2010
Exploring lactic acid bacteria diversity for better fermentation of plant-based dairy alternatives
Publisher: CSIRO Publishing
Date: 17-05-2022
DOI: 10.1071/MA22026
Abstract: Plant-based foods have risen in popularity in recent years including a number of dairy alternative products. Fermentation has the potential to support the development of innovative plant-based foods with enhanced flavour, texture and nutritional quality. Lactic acid bacteria (LAB) have been used for thousands of years to carry out fermentation of a wide variety of food substrates through production of organic acids and flavour compounds. However, LAB strains used in dairy fermentations are commonly found to be suboptimal in their metabolism of plant substrates, so efforts to identify alternative strains are needed. We provide an overview of the plant-based milk alternative category and explore screening approaches (including citizen-science efforts) to identify new LAB that hold potential in acidification and flavour formation of plant-based substrates.
Identification, characterisation and specificity of a cell wall lytic enzyme from BR11
Publisher: Oxford University Press (OUP)
Date: 09-2004
Exopolysaccharide produced by potential probiotic Enterococcus faecium MS79: Characterization, bioactivities and rheological properties influenced by salt and pH
Publisher: Elsevier BV
Date: 09-2020
Anti-staling of high-moisture starchy food: Effect of hydrocolloids, emulsifiers and enzymes on mechanics of steamed-rice cakes
Publisher: Elsevier BV
Date: 10-2018
Isolation and evaluation of anti-listeria lactococcus lactis from vegetal sources
Publisher: Springer US
Date: 26-09-2021
Enhanced uptake of potassium or glycine betaine or export of cyclic-di-AMP restores osmoresistance in a high cyclic-di-AMP Lactococcus lactis mutant
Publisher: Public Library of Science (PLoS)
Date: 03-08-2018
Genotyping of present-day and historical geobacillus species isolates from milk powders by high-resolution melt analysis of multiple variable-number tandem-repeat loci
Publisher: American Society for Microbiology
Date: 10-2012
DOI: 10.1128/AEM.01817-12
Abstract: Spores of thermophilic Geobacillus species are a common contaminant of milk powder worldwide due to their ability to form biofilms within processing plants. Genotyping methods can provide information regarding the source and monitoring of contamination. A new genotyping method was developed based on multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) in conjunction with high-resolution melt analysis (MLV-HRMA) and compared to the currently used method, randomized lified polymorphic DNA PCR (RAPD-PCR). Four VNTR loci were identified and used to genotype 46 Geobacillus isolates obtained from retailed powder and s les from 2 different milk powder processing plants. These 46 isolates were differentiated into 16 different groups using MLV-HRMA ( D = 0.89). In contrast, only 13 RAPD-PCR genotypes were identified among the 46 isolates ( D = 0.79). This new method was then used to analyze 35 isolates obtained from powders with high spore counts ( 4 spores � g −1 ) from a single processing plant together with 27 historical isolates obtained from powder s les processed in the same region of Australia 17 years ago. Results showed that three genotypes can coexist in a single processing run, while the same genotypes observed 17 years ago are present today. While certain genotypes could be responsible for powders with high spore counts, there was no correlation to specific genotypes being present in powder plants and retailed s les. In conclusion, the MLV-HRMA method is useful for genotyping Geobacillus spp. to provide insight into the prevalence and persistence of certain genotypes within milk powder processing plants.
Culture-independent bacterial community profiling of carbon dioxide treated raw milk
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.IJFOODMICRO.2016.06.015
Abstract: Due to technical simplicity and strong inhibition against the growth of psychrotrophic bacteria in milk, CO2 treatment has emerged as an attractive processing aid to increase the storage time of raw milk before downstream processing. However, it is yet to be adopted by the industry. In order to further explore the suitability of CO2 treatment for raw milk processing, the bacterial populations of carbonated raw milk collected locally from five different sources in Australia were analysed with next-generation sequencing. Growth inhibition by CO2 was confirmed, with spoilage delayed by at least 7days compared with non-carbonated controls. All non-carbonated controls were spoiled by Gammaproteobacteria, namely Pseudomonas fluorescens group bacteria, Serratia and Erwinia. Two out of the five carbonated s les shared the same spoilage bacteria as their corresponding controls. The rest of the three carbonated s les were spoiled by the lactic acid bacterium (LAB) Leuconostoc. This is consistent with higher tolerance of LAB towards CO2 and selection of LAB in meat products stored in CO2-enriched modified atmosphere packaging. No harmful bacteria were found to be selected by CO2. LAB are generally regarded as safe (GRAS), thus the selection for Leuconostoc by CO2 in some of the s les poses no safety concern. In addition, we have confirmed previous findings that 454 pyrosequencing and Illumina sequencing of 16S rRNA gene licons from the same s le yield highly similar results. This supports comparison of results obtained with the two different sequencing platforms, which may be necessary considering the imminent discontinuation of 454 pyrosequencing.
Investigation of Polycaprolactone Matrices for Intravaginal Delivery of Doxycycline
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1002/JPS.24652
Structural and functional studies of pyruvate carboxylase regulation by cyclic di-AMP in lactic acid bacteria
Publisher: Proceedings of the National Academy of Sciences
Date: 14-08-2017
Abstract: Cyclic di-3′,5′-adenosine monophosphate (c-di-AMP) is a broadly conserved bacterial second messenger that has been implicated in a wide range of cellular processes. We report here structural, biochemical, and functional studies on the inhibition of Lactococcus lactis pyruvate carboxylase (LlPC) by c-di-AMP. The compound has a distinct binding mode in LlPC compared with that in Listeria monocytogenes PC. Mutations of residues in the binding site can abolish c-di-AMP inhibition. LlPC is required for efficient milk acidification through its essential role in aspartate biosynthesis. The aspartate pool in L. lactis is negatively regulated by c-di-AMP, and high aspartate levels can be restored by a c-di-AMP–insensitive LlPC. LlPC has high intrinsic catalytic activity and is insensitive to acetyl-CoA activation, in contrast to other PCs.
New insights into cooked rice quality by measuring modulus, adhesion and cohesion at the level of an individual rice grain
Publisher: Elsevier BV
Date: 2019
Potential Probiotic Pediococcus pentosaceus M41 Modulates Its Proteome Differentially for Tolerances Against Heat, Cold, Acid, and Bile Stresses
Publisher: Frontiers Media SA
Date: 13-10-2021
DOI: 10.3389/FMICB.2021.731410
Abstract: Probiotics containing functional food confer health benefits in addition to their nutritional properties. In this study, we have evaluated the differential proteomic responses of a potential novel probiotic Pediococcus pentosaceus M41 under heat, cold, acid, and bile stress conditions. We identified stress response proteins that could provide tolerances against these stresses and could be used as probiotic markers for evaluating stress tolerance. Pediococcus pentosaceus M41 was exposed for 2 h to each condition: 50°C (heat stress), 4°C (cold stress), pH 3.0 (acid stress) and 0.05% bile (bile stress). Proteomic analysis was carried out using 2D-IEF SDS PAGE and LC-MS/MS. Out of 60 identified proteins, 14 upregulated and 6 downregulated proteins were common among all the stress conditions. These proteins were involved in different biological functions such as translation-related proteins, carbohydrate metabolism (phosphoenolpyruvate phosphotransferase), histidine biosynthesis (imidazole glycerol phosphate synthase) and cell wall synthesis (tyrosine-protein kinase CapB). Proteins such as polysaccharide deacetylase, lactate oxidase, transcription repressor NrdR, dihydroxyacetone kinase were upregulated under three out of the four stress conditions. The differential expression of these proteins might be responsible for tolerance and protection of P. pentosaceus M41 against different stress conditions.
Cyclic-di-AMP signalling in lactic acid bacteria
Publisher: Oxford University Press (OUP)
Date: 05-2023
Abstract: Cyclic dimeric adenosine monophosphate (cyclic-di-AMP) is a nucleotide second messenger present in Gram-positive bacteria, Gram-negative bacteria and some Archaea. The intracellular concentration of cyclic-di-AMP is adjusted in response to environmental and cellular cues, primarily through the activities of synthesis and degradation enzymes. It performs its role by binding to protein and riboswitch receptors, many of which contribute to osmoregulation. Imbalances in cyclic-di-AMP can lead to pleiotropic phenotypes, affecting aspects such as growth, biofilm formation, virulence, and resistance to osmotic, acid, and antibiotic stressors. This review focuses on cyclic-di-AMP signalling in lactic acid bacteria (LAB) incorporating recent experimental discoveries and presenting a genomic analysis of signalling components from a variety of LAB, including those found in food, and commensal, probiotic, and pathogenic species. All LAB possess enzymes for the synthesis and degradation of cyclic-di-AMP, but are highly variable with regards to the receptors they possess. Studies in Lactococcus and Streptococcus have revealed a conserved function for cyclic-di-AMP in inhibiting the transport of potassium and glycine betaine, either through direct binding to transporters or to a transcriptional regulator. Structural analysis of several cyclic-di-AMP receptors from LAB has also provided insights into how this nucleotide exerts its influence.
Survivability of probiotics encapsulated in alginate gel microbeads using a novel impinging aerosols method
Publisher: Elsevier BV
Date: 31-01-2011
DOI: 10.1016/J.IJFOODMICRO.2010.12.007
Abstract: Encapsulation of probiotic bacteria in cross-linked alginate beads is of major interest for improving the survivability in harsh acid and bile environment and also in food matrices. Alginate micro beads (10-40 μm) containing the probiotics Lactobacillus rhamnosus GG and Lactobacillus acidophilus NCFM were produced by a novel technique based on dual aerosols of alginate solution and CaCl(2) cross linking solution. Extruded macro beads (approximately 2mm diameter) produced by the conventional method and micro beads produced by novel aerosols technique offered comparable protection to L. rhamnosus in high acid and bile environment. Chitosan coating of micro beads resulted in a significant increase in survival time of L. rhamnosus from 40 to 120 min in acid condition and the reduction in cell numbers was confined to 0.94 log over this time. Alginate macro beads are more effective than micro beads in protecting L. acidophilus against high acid and bile. Chitosan coating of micro beads resulted in similar protection to L. acidophilus in macro beads in acid and extended the survival time from 90 to at least 120 min. Viability of this organism in micro beads was 3.5 log after 120 min. The continuous processing capability and scale-up potential of the dual aerosol technique offers potential for an efficient encapsulation of probiotics in very small alginate micro beads below sensorial detection limits while still being able to confer effective protection in acid and bile environment.
Quantification of acid–base interactions based on contact angle measurement allows XDLVO predictions to attachment of Campylobacter jejuni but not Salmonella
Publisher: Elsevier BV
Date: 07-2011
DOI: 10.1016/J.MIMET.2011.04.005
Abstract: Acid-base (AB) interactions play the most important role in bacterial attachment to surfaces and can be quantified based on electron donor/electron acceptor data from contact angle measurement (CAM) according to the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. It follows that the XDLVO theory could fail to explain attachment numbers if differences in AB interactions between strains are not apparent by CAM. This study aimed to investigate the validity of the above assumptions by comparing empirical data on attachment of six bacterial strains (three strains of C ylobacter jejuni and three strains of Salmonella) to stainless steel and XDLVO theory predictions. A significant difference (P<0.05) in AB interactions, apparent by CAM, between C. jejuni strains allowed prediction of attachment of this species by the XDLVO theory. However, the theory failed to explain the attachment numbers for Salmonella due to similar AB interactions, as established by CAM, between the three Salmonella strains. Qualitative analysis of AB interactions by microbial adhesion to solvents (MATS) revealed a significant difference (P<0.05) in electron donor property between the three Salmonella strains suggesting that these strains may differ with respect to AB interactions. No significant correlation with respect to electron donor property (P=0.502, r(2)=12%) was apparent between CAM and MATS. These data suggest that CAM may not always reflect exactly AB interactions and that the difference in the outcomes from MATS and CAM should be considered when the XDLVO theory is used to predict bacterial attachment to surfaces.
The impact of variable high pressure treatments and/or cooking of rice on bacterial populations after storage using culture-independent analysis
Publisher: Elsevier BV
Date: 10-2018
Onward and [K + ]Upward: a New Potassium Importer under the Spell of Cyclic di-AMP
Publisher: American Society for Microbiology
Date: 15-05-2019
DOI: 10.1128/JB.00150-19
Abstract: Cyclic di-AMP (c-di-AMP) is a second messenger which plays a major role in osmotic homeostasis in bacteria. In work by Quintana et al. (I.
Draft Genome Comparison of Representatives of the Three Dominant Genotype Groups of Dairy Bacillus licheniformis Strains
Publisher: American Society for Microbiology
Date: 06-2014
DOI: 10.1128/AEM.00065-14
Abstract: The spore-forming bacterium Bacillus licheniformis is a common contaminant of milk and milk products. Strains of this species isolated from dairy products can be differentiated into three major groups, namely, G, F1, and F2, using random lification of polymorphic DNA (RAPD) analysis however, little is known about the genomic differences between these groups and the identity of the fragments that make up their RAPD profiles. In this work we obtained high-quality draft genomes of representative strains from each of the three RAPD groups (designated strain G-1, strain F1-1, and strain F2-1) and compared them to each other and to B. licheniformis ATCC 14580 and Bacillus subtilis 168. Whole-genome comparison and multilocus sequence typing revealed that strain G-1 contains significant sequence variability and belongs to a lineage distinct from the group F strains. Strain G-1 was found to contain genes coding for a type I restriction modification system, urease production, and bacitracin synthesis, as well as the 8-kbp plasmid pFL7, and these genes were not present in strains F1-1 and F2-1. In agreement with this, all isolates of group G, but no group F isolates, were found to possess urease activity and antimicrobial activity against Micrococcus . Identification of RAPD band sequences revealed that differences in the RAPD profiles were due to differences in gene lengths, 3′ ends of predicted primer binding sites, or gene presence or absence. This work provides a greater understanding of the phylogenetic and phenotypic differences observed within the B. licheniformis species.
Heat, cold, acid, and bile salt induced differential proteomic responses of a novel potential probiotic Lactococcus garvieae C47 isolated from camel milk
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.FOODCHEM.2022.133774
Abstract: Probiotics encounter various stresses during food processing and digestion. This study evaluated the differential proteomic responses of a newly identified potential probiotic lactic acid bacteria, Lactococcus garvieae, isolated from camel milk. Lc. garvieae C47 was exposed to heat, cold, acid, and bile conditions, and stress-responsive proteins were identified. The proteomic analysis was done using 2D-IEF SDS PAGE and nano-LC-MS/MS. Out of 91 differentially expressed proteins, 20 upregulated and 27 downregulated proteins were shared among the stresses. The multivariate data analysis revealed abundance of elongation factor Ts (spot C42), uridine phosphorylase, fructose-bisphosphate aldolase, peptidase T, cobalt ECF transporter T component CbiQ, UDP-N-acetylmuramate-l-alanine ligase, uncharacterized protein, aspartokinase, chaperone protein DnaK, IGP synthase cyclase subunit, probable nicotinate-nucleotide adenylyltransferase, NADH-quinone oxidoreductase, holo-[acyl-carrier-protein] synthase, l-lactate dehydrogenase, and uncharacterized protein. The maximum number of differentially expressed proteins belonged to carbohydrate and protein metabolism, which indicates Lc. garvieae shifts towards growth and energy metabolism for resistance against stress conditions.
Development of intra-vaginal matrices from polycaprolactone for sustained release of antimicrobial agents
Publisher: SAGE Publications
Date: 08-06-2013
Abstract: Microporous poly(ɛ-caprolactone) matrices were loaded with an antibacterial agent, ciprofloxacin and an antifungal agent, miconazole nitrate, respectively, for investigations of their potential as controlled vaginal delivery devices. Ciprofloxacin loadings up to 15% w/w could be obtained by increasing the drug content of the poly(ɛ-caprolactone) solution, while the actual loadings of miconazole were much lower (1–3% w/w) due to drug partition into methanol during the solvent extraction. The kinetics of ciprofloxacin release in simulated vaginal fluid at 37℃ were characterised by a small burst release phase in the first 24 h, low drug release up to 7 days (10%) and gradual release of up to 80% of the drug content by day 30. Meanwhile, the release kinetics of miconazole-loaded matrices could be effectively described by the Higuchi model with 100% drug release from the highest loaded matrices (3.2% w/w) in 13 days. Ciprofloxacin or miconazole released over 30 and 13 days, respectively, from poly(ɛ-caprolactone) matrices into simulated vaginal fluid retained high levels of antimicrobial activity in excess of 80% of the activity of the free drug. This study confirms the potential of poly(ɛ-caprolactone) matrices for delivering antimicrobial agents in the form of an intra-vaginal device.
Evaluating the potential impact of proton carriers on syntrophic propionate oxidation
Publisher: Springer Science and Business Media LLC
Date: 16-12-2015
DOI: 10.1038/SREP18364
Abstract: Anaerobic propionic acid degradation relies on interspecies electron transfer (IET) between propionate oxidisers and electron acceptor microorganisms, via either molecular hydrogen, formate or direct transfers. We evaluated the possibility of stimulating direct IET, hence enhancing propionate oxidation, by increasing availability of proton carriers to decrease solution resistance and reduce pH gradients. Phosphate was used as a proton carrying anion and chloride as control ion together with potassium as counter ion. Propionic acid consumption in anaerobic granules was assessed in a square factorial design with ratios (1:0, 2:1, 1:1, 1:2 and 0:1) of total phosphate (TP) to Cl − , at 1X, 10X and 30X native conductivity (1.5 mS.cm −1 ). Maximum specific uptake rate, half saturation and time delay were estimated using model-based analysis. Community profiles were analysed by fluorescent in situ hybridisation and 16S rRNA gene pyrosequencing. The strongest performance was at balanced (1:1) ratios at 10X conductivity where presumptive propionate oxidisers namely Syntrophobacter and Candidatus Cloacamonas were more abundant. There was a shift from Methanobacteriales at high phosphate, to Methanosaeta at low TP:Cl ratios and low conductivity. A lack of response to TP and low percentage of presumptive electroactive organisms suggested that DIET was not favoured under the current experimental conditions.
Plasmid-borne blaSHV genes in Klebsiella pneumoniae are associated with strong promoters
Publisher: Oxford University Press (OUP)
Date: 12-09-2009
DOI: 10.1093/JAC/DKP338
Abstract: Extended-spectrum beta-lactamases (ESBLs) belonging to the SHV family remain a major cause of ESBL-positive phenotypes in Klebsiella pneumoniae. The bla(SHV) gene is a normal constituent of the K. pneumoniae chromosome. However, most ESBL-encoding bla(SHV) genes found in K. pneumoniae are plasmid borne. The objective was to determine the contribution of promoter variants to the expression of plasmid-borne bla(SHV) genes. K. pneumoniae clinical isolates were analysed for the presence of IS26 insertions characteristic of plasmid-borne bla(SHV), and differences in their bla(SHV) promoter sequences and expression levels. A high resolution melting (HRM)-based method for rapid promoter analysis was developed. An IS26 insertion characteristic of the plasmid-borne bla(SHV-1)/bla(SHV-2)/bla(SHV-5) family was 100% linked to a promoter mutated in the -10 region, a mutation previously only found on the chromosome. The mutation was shown by real-time reverse transcriptase PCR to be associated with increased bla(SHV) expression. Plasmid-borne bla(SHV) is associated with strong promoters. It is likely that an SHV-dependent ESBL-positive phenotype requires both a strong promoter and a coding sequence mutation. An HRM assay can indicate bla(SHV) expression.
An overview of microbial mitigation strategies for acrylamide: Lactic acid bacteria, yeast, and cell-free extracts
Publisher: Elsevier BV
Date: 05-2021
A genetic diversity study of antifungal Lactobacillus plantarum isolates
Publisher: Elsevier BV
Date: 02-2017
Peptide Surface Display and Secretion Using Two LPXTG-Containing Surface Proteins from Lactobacillus fermentum BR11
Publisher: American Society for Microbiology
Date: 10-2003
DOI: 10.1128/AEM.69.10.5855-5863.2003
Abstract: A locus encoding two repetitive proteins that have LPXTG cell wall anchoring signals from Lactobacillus fermentum BR11 has been identified by using an antiserum raised against whole L. fermentum BR11 cells. The first protein, Rlp, is similar to the Rib surface protein from Streptococcus agalactiae , while the other protein, Mlp, is similar to the mucus binding protein Mub from Lactobacillus reuteri . It was shown that multiple copies of mlp exist in the genome of L. fermentum BR11. Regions of Rlp, Mlp, and the previously characterized surface protein BspA were used to surface display or secrete heterologous peptides in L. fermentum . The peptides tested were 10 amino acids of the human cystic fibrosis transmembrane regulator protein and a six-histidine epitope (His 6 ). The BspA promoter and secretion signal were used in combination with the Rlp cell wall sorting signal to express, export, and covalently anchor the heterologous peptides to the cell wall. Detection of the cell surface protein fusions revealed that Rlp was a significantly better surface display vector than BspA despite having lower cellular levels (0.7 mg per liter for the Rlp fusion compared with 4 mg per liter for the BspA fusion). The mlp promoter and encoded secretion signal were used to express and export large (328-kDa at 10 mg per liter) and small (27-kDa at 0.06 mg per liter) amino-terminal fragments of the Mlp protein fused to the His 6 and CFTR peptides or His 6 peptide, respectively. Therefore, these newly described proteins from L. fermentum BR11 have potential as protein production and targeting vectors.
Inhibition of Staphylococcus aureus Growth on Tellurite-Containing Media by Lactobacillus reuteri Is Dependent on CyuC and Thiol Productio
Publisher: American Society for Microbiology
Date: 02-2007
DOI: 10.1128/AEM.02100-06
Abstract: Lactobacillus reuteri inhibits Staphylococcus aureus growth on Baird-Parker agar. This activity required the presence of tellurite and was not shared with other lactic acid bacteria or an L. reuteri mutant defective in cystine metabolism. Secreted products generated from L. reuteri cystine metabolism and thiols were shown to augment tellurite toxicity.
Updates on understanding of probiotic lactic acid bacteria responses to environmental stresses and highlights on proteomic analyses
Publisher: Wiley
Date: 14-04-2020
Methyl jasmonate enhances biocontrol efficacy of Rhodotorula glutinis to postharvest blue mold decay of pears
Publisher: Elsevier BV
Date: 15-12-2009
Volatile sulfur compounds produced by probiotic bacteria in the presence of cysteine or methionine
Publisher: Oxford University Press (OUP)
Date: 04-2009
Random mutagenesis identifies novel genes involved in the secretion of antimicrobial, cell wall-lytic enzymes by Lactococcus lactis
Publisher: American Society for Microbiology
Date: 15-12-2008
DOI: 10.1128/AEM.00767-08
Abstract: Lactococcus lactis is a gram-positive bacterium that is widely used in the food industry and is therefore desirable as a candidate for the production and secretion of recombinant proteins. Previously, we generated a L. lactis strain that expressed and secreted the antimicrobial cell wall-lytic enzyme lysostaphin. To identify lactococcal gene products that affect the production of lysostaphin, we isolated and characterized mutants generated by random transposon mutagenesis that had altered lysostaphin activity. Out of 35,000 mutants screened, only one with no lysostaphin activity was identified, and it was found to contain an insertion in the lysostaphin expression cassette. Ten mutants with higher lysostaphin activity contained insertions in only four different genes, which encode an uncharacterized putative transmembrane protein (llmg_0609) (three mutants), an enzyme catalyzing the first step in peptidoglycan biosynthesis ( murA2 ) (five mutants), a putative regulator of peptidoglycan modification ( trmA ) (one mutant), and an uncharacterized enzyme possibly involved in ubiquinone biosynthesis (llmg_2148) (one mutant). These mutants were found to secrete larger amounts of lysostaphin than the control strain (MG1363[ lss ]), and the greatest increase in secretion was 9.8- to 16.1-fold, for the llmg_0609 mutants. The lysostaphin-oversecreting llmg_0609, murA2 , and trmA mutants were also found to secrete larger amounts of another cell wall-lytic enzyme (the Listeria monocytogenes bacteriophage endolysin Ply511) than the control strain, indicating that the phenotype is not limited to lysostaphin.
New Australian guidelines for the treatment of alcohol problems: an overview of recommendations
Publisher: AMPCo
Date: 03-10-2021
DOI: 10.5694/MJA2.51254
Purified 1′acetoxychavicol acetate (1′ACA) from galangal spice affects membrane fatty acid composition and triggers a cell envelope stress response in Staphylococcus aureus
Publisher: Elsevier BV
Date: 03-2012
Cyclic-di-AMP synthesis by the diadenylate cyclase CdaA is modulated by the peptidoglycan biosynthesis enzyme GlmM in L actococcus lactis
Publisher: Wiley
Date: 15-12-2015
DOI: 10.1111/MMI.13281
Abstract: The second messenger cyclic-di-adenosine monophosphate (c-di-AMP) plays important roles in growth, virulence, cell wall homeostasis, potassium transport and affects resistance to antibiotics, heat and osmotic stress. Most Firmicutes contain only one c-di-AMP synthesizing diadenylate cyclase (CdaA) however, little is known about signals and effectors controlling CdaA activity and c-di-AMP levels. In this study, a genetic screen was employed to identify components which affect the c-di-AMP level in Lactococcus. We characterized suppressor mutations that restored osmoresistance to spontaneous c-di-AMP phosphodiesterase gdpP mutants, which contain high c-di-AMP levels. Loss-of-function and gain-of-function mutations were identified in the cdaA and gdpP genes, respectively, which led to lower c-di-AMP levels. A mutation was also identified in the phosphoglucosamine mutase gene glmM, which is commonly located within the cdaA operon in bacteria. The glmM I154F mutation resulted in a lowering of the c-di-AMP level and a reduction in the key peptidoglycan precursor UDP-N-acetylglucosamine in L. lactis. C-di-AMP synthesis by CdaA was shown to be inhibited by GlmM(I154F) more than GlmM and GlmM(I154F) was found to bind more strongly to CdaA than GlmM. These findings identify GlmM as a c-di-AMP level modulating protein and provide a direct connection between c-di-AMP synthesis and peptidoglycan biosynthesis.
Heat Resistance and Salt Hypersensitivity in Lactococcus lactis Due to Spontaneous Mutation of llmg_1816 ( gdpP ) Induced by High-Temperat
Publisher: American Society for Microbiology
Date: 11-2012
DOI: 10.1128/AEM.02316-12
Abstract: During construction of several gene deletion mutants in Lactococcus lactis MG1363 which involved a high-temperature (37.5°C) incubation step, additional spontaneous mutations were observed which resulted in stable heat resistance and in some cases salt-hypersensitive phenotypes. Whole-genome sequencing of one strain which was both heat resistant and salt hypersensitive, followed by PCR and sequencing of four other mutants which shared these phenotypes, revealed independent mutations in llmg_1816 in all cases. This gene encodes a membrane-bound stress signaling protein of the GdpP family, members of which exhibit cyclic dimeric AMP (c-di-AMP)-specific phosphodiesterase activity. Mutations were predicted to lead to single amino acid substitutions or protein truncations. An independent llmg_1816 mutant (Δ1816), created using a suicide vector, also displayed heat resistance and salt hypersensitivity phenotypes which could be restored to wild-type levels following plasmid excision. L. lactis Δ1816 also displayed improved growth in response to sublethal concentrations of penicillin G. High-temperature incubation of a wild-type industrial L. lactis strain also resulted in spontaneous mutation of llmg_1816 and heat-resistant and salt-hypersensitive phenotypes, suggesting that this is not a strain-specific phenomenon and that it is independent of a plasmid integration event. Acidification of milk by the llmg_1816 -altered strain was inhibited by lower salt concentrations than the parent strain. This study demonstrates that spontaneous mutations can occur during high-temperature growth of L. lactis and that inactivation of llmg_1816 leads to temperature resistance and salt hypersensitivity.
Stability of active prophages in industrial Lactococcus lactis strains in the presence of heat, acid, osmotic, oxidative and antibiotic stressors
Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.IJFOODMICRO.2015.12.012
Abstract: Lactococcus lactis is a starter bacterium commonly used in cheese making where it has an important role in acid-mediated curd formation as well as the development of flavour compounds. Industrial L. lactis strains can harbour one or more inducible prophages which when induced can affect cell growth and possibly lead to cell lysis. This is undesirable during growth and fermentation, but can beneficially lead to faster release of enzymes during cheese ripening. Lactococci can encounter multiple stress inducing conditions during the production of cheese, such as low and high temperatures, low pH, high osmotic pressure and long-term incubation. In this study, we tested the effect of these industrial stressors on prophage induction in two cheese making L. lactis subsp. cremoris strains (ASCC890049 and ASCC890310) as well as the laboratory strain L. lactis MG1363. Firstly, in order to identify inducible prophages in these strains we exposed them to the prophage inducing chemical mitomycin C (MMC) for 1 and 2h and then subjected the total genomic DNA to next-generation Illumina sequencing. Mapping of sequence reads back to the genome sequences revealed regions which contained a much higher fold coverage indicating DNA replication. These regions were lified by up to 332-fold per cell (relative to the control tufA gene) and were identified as having similarities to different subgroups of P335 phages including MG-5, TP901-1, ul36.k1, bIL286, TP712 and BK5-T. Next, quantitative PCR was used to confirm the strong induction of prophages by MMC and then determine the copy number of the inducible prophages following exposure to various growth inhibitory levels of HCl, lactic acid, high temperature, NaCl, hydrogen peroxide and bacitracin. With the exception of a slight induction (2 to 4-fold) with hydrogen peroxide and long-term incubation after 21days in one industrial strain, none of the other stressors induced prophage DNA replication. These findings show that the repression system that maintains prophages in the dormant state in cheese making lactococcal strains is very tight and that several stressors encountered singularly are not predicted to be major inducers of prophage activation.
The genetic basis underlying variation in production of the flavour compound diacetyl by Lactobacillus rhamnosus strains in milk
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.IJFOODMICRO.2017.10.029
Abstract: Diacetyl and the closely related compound acetoin impart desirable buttery flavour and odour to many foods including cheese and are generated through the metabolism of citrate by lactic acid bacteria (LAB). To increase the levels of these compounds, adjunct cultures capable of producing them can be added to cheese fermentations. In this study, we compared the diacetyl and acetoin producing abilities of 13 Lactobacillus rhamnosus strains from cheese sources. Diacetyl and acetoin production was found to be a common feature of Lb. rhamnosus grown in milk, with 12 strains producing these compounds. Whole genome sequencing of four strains revealed that genes encoding the citrate metabolising pathway present in other LAB are conserved in Lb. rhamnosus. One strain was, however, totally defective in diacetyl and acetoin production. This was likely due to an inability to produce the diacetyl/acetoin precursor compound acetolactate resulting from a frameshift mutation in the acetolactate synthase (als) gene. Complementation of this defective strain with a complete als gene from a diacetyl producing strain restored production of diacetyl and acetoin to levels equivalent to naturally high producing strains. Introduction of the same als-containing plasmid into the probiotic Lb. rhamnosus strain GG also increased diacetyl and acetoin levels. In model cheesemaking experiments, the als-complemented strain produced very high levels of diacetyl and acetoin over 35days of ripening. These findings identify the genetic basis for natural variation in production of a key cheese flavour compound in Lb. rhamnosus strains.
Characterisation of Lactococcus lactis isolates from herbs, fruits and vegetables for use as biopreservatives against Listeria monocytogenes in cheese
Publisher: Elsevier BV
Date: 03-2018
BspA (CyuC) in Lactobacillus fermentum BR11 Is a Highly Expressed High-Affinity L-Cystine-Binding Protein
Publisher: Springer Science and Business Media LLC
Date: 2005
DOI: 10.1007/S00284-004-4408-2
Abstract: The BspA protein of Lactobacillus fermentum BR11 (BR11) is a cell envelope constituent that is similar to known solute-binding proteins and putative adhesins. BspA is required for L-cystine uptake and oxidative defense and is likely to be an L-cystine-binding protein. The aim of this study was to directly measure L-cystine-BspA binding and BspA expression. De-energized BR11 cells bound radiolabelled L-cystine with a Kd of 0.2 microM. A bspA mutant could not bind L-cystine. L-cystine-BR11 binding was unaffected by large excesses of L-glutamine, L-methionine, or collagen, indicating L-cystine specificity. BR11 and the bspA mutant were identical in their abilities to bind L-cysteine, indicating that L-cysteine is not a BspA ligand. BspA expression levels were deduced from radiolabelled L-cystine binding and it was found that there are 1-2 x 10(5) BspA molecules per cell, and that expression is slightly higher under oxidizing conditions. It is proposed that BspA be renamed CyuC.
Cyclic di-AMP Oversight of Counter-Ion Osmolyte Pools Impacts Intrinsic Cefuroxime Resistance in Lactococcus lactis
Publisher: American Society for Microbiology
Date: 27-04-2021
Abstract: The bacterial second messenger cyclic di-AMP (c-di-AMP) is a global regulator of potassium homeostasis and compatible solute uptake in many Gram-positive bacteria, making it essential for osmoregulation. The role that c-di-AMP plays in β-lactam resistance, however, is unclear despite being first identified a decade ago.
Evaluation of the fermentation potential of lactic acid bacteria isolated from herbs, fruits and vegetables as starter cultures in nut-based milk alternatives
Publisher: Elsevier BV
Date: 06-2023
Learning about foodborne pathogens: Evaluation of student perceptions of group project work in a food microbiology course: Research in food science education
Publisher: Wiley
Date: 16-09-2009
Isolation, identification, and potential probiotic characterization of isolated lactic acid bacteria and in vitro investigation of the cytotoxicity, antioxidant, and antidiabetic activities in ferment
Publisher: Springer Science and Business Media LLC
Date: 05-11-2019
DOI: 10.1186/S12934-019-1239-1
Abstract: Probiotic bacteria can provide health benefits when delivered in functional foods. This study involved isolation of lactic acid bacteria (LAB) from traditionally dried and salted anchovy fish and characterization of their survival in simulated gastrointestinal digestion. Promising strains were used to prepare fermented fish sausages which were then evaluated for cytotoxicity activity against two cancer cell-lines, antidiabetic activity as determined by α-amylase and α-glucosidase inhibition, and antioxidant and proteolytic activities in vitro, as compared to non-fermented control sausages. Out of 85 LAB obtained, 13 isolates with high tolerance to simulated gastrointestinal digestion were obtained, which were identified as Enterococcus spp. Four E. faecium strains, one E. faecalis , and one E. durans were used separately to make fermented fish sausages. The α-amylase and α-glucosidase inhibition from fish sausages fermented by Enterococcus spp. ranged from 29.2 to 68.7% and 23.9 to 41.4%, respectively, during 21 days of storage. The cytotoxicity activities against Caco 2 and MCF-7 cells of fish sausages fermented with Enterococcus spp. ranged from 18.0 to 24% and 13.9 to 27.9%, respectively. Cytotoxicity activities correlated positively with proteolysis and antioxidant activities, α-amylase and α-glucosidase inhibition activities, but negatively with the pH in fermented fish sausages. Strains also exhibited antimicrobial activity against foodborne pathogens and presented no significant concerns with regards to antibiotic resistance or virulence gene content. Fish sausages fermented by potential probiotic isolates of Enterococcus spp. from dried fish had valuable health-promoting benefits compared with non-fermented control sausages.
The impact of commercial prebiotics on the growth, survival and nisin production by Lactococcus lactis 537 in milk
Publisher: Elsevier BV
Date: 02-2021
Engineering Escherichia coli for propionic acid production through the Wood–Werkman cycle
Publisher: Wiley
Date: 16-10-2019
DOI: 10.1002/BIT.27182
Abstract: Native to propionibacteria, the Wood-Werkman cycle enables propionate production via succinate decarboxylation. Current limitations in engineering propionibacteria strains have redirected attention toward the heterologous production in model organisms. Here, we report the functional expression of the Wood-Werkman cycle in Escherichia coli to enable propionate and 1-propanol production. The initial proof-of-concept attempt showed that the cycle can be used for production. However, production levels were low (0.17 mM). In silico optimization of the expression system by operon rearrangement and ribosomal-binding site tuning improved performance by fivefold. Adaptive laboratory evolution further improved performance redirecting almost 30% of total carbon through the Wood-Werkman cycle, achieving propionate and propanol titers of 9 and 5 mM, respectively. Rational engineering to reduce the generation of byproducts showed that lactate (∆ldhA) and formate (∆pflB) knockout strains exhibit an improved propionate and 1-propanol production, while the ethanol (∆adhE) knockout strain only showed improved propionate production.
Control of Listeria monocytogenes on ready-to-eat ham and fresh cut iceberg lettuce using a nisin containing Lactococcus lactis fermentate
Publisher: Elsevier BV
Date: 2021
Mutations in Multidrug Efflux Homologs, Sugar Isomerases, and Antimicrobial Biosynthesis Genes Differentially Elevate Activity of the ς
X
and ς
W
Publisher:
American Society for Microbiology
Date:
15-09-2000
DOI:
10.1128/JB.182.18.5202-5210.2000
Abstract: The ς X and ς W extracytoplasmic function sigma factors regulate more than 40 genes in Bacillus subtilis . ς W activates genes which function in detoxification and the production of antimicrobial compounds, while ς X activates functions that modify the cell envelope. Transposon mutagenesis was used to identify loci which negatively regulate ς W or ς X as judged by up-regulation from the autoregulatory promoter site P W or P X . Fourteen insertions that activate P W were identified. The largest class of insertions are likely to affect transport. These include insertions in genes encoding two multidrug efflux protein homologs ( yqgE and yulE ), a component of the oligopeptide uptake system ( oppA ), and two transmembrane proteins with weak similarity to transporters ( yhdP and yueF ). Expression from P W is also elevated as a result of inactivation of at least one member of the ς W regulon ( ysdB ), an ArsR homolog ( yvbA ), a predicted rhamnose isomerase ( yulE ), and a gene ( pksR ) implicated in synthesis of difficidin, a polyketide antibiotic. In a parallel screen, we identified seven insertions that up-regulate P X . Remarkably, these insertions were in functionally similar genes, including a multidrug efflux homolog ( yitG ), a mannose-6-phosphate isomerase gene ( yjdE ), and loci involved in antibiotic synthesis ( srfAB and possibly yogA and yngK ). Significantly, most insertions that activate P W have little or no effect on P X , and conversely, insertions that activate P X have no effect on P W . This suggests that these two regulons respond to distinct sets of molecular signals which may include toxic molecules which are exported, cell density signals, and antimicrobial compounds.
Invited review: Characterization of new probiotics from dairy and nondairy products—Insights into acid tolerance, bile metabolism and tolerance, and adhesion capability
Publisher: American Dairy Science Association
Date: 08-2021
Lactobacillus helveticus: Health effects, current applications, and future trends in dairy fermentation
Publisher: Elsevier BV
Date: 06-2023
Comparison between cage and free-range egg production on microbial composition, diversity and the presence of Salmonella enterica
Publisher: Elsevier BV
Date: 08-2021
Unravelling the aroma and flavour of algae for future food applications
Publisher: Elsevier BV
Date: 08-2023
What bacteria are living in my food?: An open-ended practical series involving identification of unknown foodborne bacteria using molecular techniques
Publisher: Wiley
Date: 09-2011
DOI: 10.1002/BMB.20532
Abstract: This open-ended practical series titled "Molecular Identification of Unknown Food Bacteria" which extended over a 6-week period was designed with the aims of giving students an opportunity to gain an understanding of naturally occurring food bacteria and skills in contemporary molecular methods using real food s les. The students first isolated two unknown bacterial strains from two food sources from which they extracted DNA and performed PCR targeting the 16S rRNA gene. Gel electrophoresis was used to analyze both genomic DNA preparations and PCR products. Following purification of PCR products, DNA sequencing was carried out and sequence trace quality was analyzed. The students successfully identified the two unknown bacteria using the BLAST search engine and a wide variety of different organisms were found. Assessment of their understanding of the procedure and ability to explain their findings using supporting primary research literature was via an in idually prepared written report. Feedback from students over 2 years (n = 52) in a questionnaire revealed that the practical series was an engaging learning experience and lead to perceived improvements in knowledge of molecular techniques and bioinformatics and also about commonly occurring bacteria in foods.
Activity of HIV entry and fusion inhibitors expressed by the human vaginal colonizing probiotic Lactobacillus reuteri RC-14
Publisher: Hindawi Limited
Date: 2007
DOI: 10.1111/J.1462-5822.2006.00772.X
Abstract: Novel therapeutic approaches are needed to combat the rapid increase in HIV sexual transmission in women. The probiotic organism Lactobacillus reuteri RC-14 which safely colonizes the human vagina and prevents microbial infections, has been genetically modified to produce anti-HIV proteins which were capable of blocking the three main steps of HIV entry into human peripheral blood mononuclear cells. The HIV entry or fusion inhibitors were fused to the native expression and secretion signals of BspA, Mlp or Sep in L. reuteri RC-14 and the expression cassettes were stably inserted into the chromosome. L. reuteri RC-14 expressed the HIV inhibitors in cell wall-associated and secreted forms. L. reuteri RC-14 expressing CD4D1D2-antibody-like fusion proteins were able to bind single or dual tropic coreceptor-using HIV-1 primary isolates. This is the first study to show that a well-documented and proven human vaginal probiotic strain can express potent functional viral inhibitors, which may potentially lower the sexual transmission of HIV.
Co-culture with Acinetobacter johnsonii enhances benzalkonium chloride resistance in Salmonella enterica via triggering lipid A modifications
Publisher: Elsevier BV
Date: 11-2022
DOI: 10.1016/J.IJFOODMICRO.2022.109905
Abstract: Salmonella enterica is one of the leading causes of foodborne gastroenteritis worldwide. In the food production environment, many bacterial species co-exist on surfaces in biofilm structures, which can act as reservoirs of microbial contamination of food products. Polymicrobial biofilms have been shown to have greater tolerance to antimicrobials, such as disinfectants, however the mechanistic basis of this is poorly understood. In this study, S. enterica subsp. enterica serovar Liverpool was co-cultured in mixed-species biofilms with bacteria isolated from the food production environment and challenged with the cationic biocide disinfectant, benzalkonium chloride (BC). Co-culture with the common environmental bacterium Acinetobacter johnsonii resulted in >200-fold higher resistance of S. Liverpool to BC, compared to mono-culture biofilms. The transcriptional response of S. enterica to biofilm co-culture was determined using a dual RNA-seq strategy. Genes controlled by the PhoPQ and PmrAB two-component systems, involved in lipid A modification and associated with cationic antimicrobial peptide resistance (CAMP) of S. Liverpool, were significantly upregulated. Deletion of either the phoP or pmrA genes resulted in an increase in susceptibility to BC, suggesting that activation of their regulons during co-culture enhances BC resistance. S. Liverpool lipid A profiles changed significantly upon co-culturing, with greater incorporation of both phosphoethanolamine and palmitate, which was dependent upon activation of PhoPQ and PmrAB. We conclude that when grown in the presence of A. johnsonii, S. Liverpool increases its tolerance to cationic BC disinfection by remodelling its cell envelope including reducing the net negative charge of lipid A and increasing lipid A acyl density.
Evaluation of Lactobacillus rhamnosus GG and Lactobacillus acidophilus NCFM encapsulated using a novel impinging aerosol method in fruit food products
Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.IJFOODMICRO.2012.04.025
Abstract: This study investigated the effect of microencapsulation on the survival of Lactobacillus rhamnosus GG and Lactobacillus acidophilus NCFM and their acidification in orange juice at 25°C for nine days and at 4°C over thirty five days of storage. Alginate micro beads (10-40 μm) containing the probiotics were produced by a novel dual aerosol method of alginate and CaCl(2) cross linking solution. Unencapsulated L. rhamnosus GG was found to have excellent survivability in orange juice at both temperatures. However unencapsulated L. acidophilus NCFM showed significant reduction in viability. Encapsulation of these two bacteria did not significantly enhance survivability but did reduce acidification at 25°C and 4°C. In agreement with this, encapsulation of L. rhamnosus GG also reduced acidification in pear and peach fruit-based foods at 25°C, however at 4°C difference in pH was insignificant between free and encapsulated cells. In conclusion, L. rhamnosus GG showed excellent survival in orange juice and microencapsulation has potential in reducing acidification and possible negative sensory effects of probiotics in orange juice and other fruit-based products.
Replenishing the cyclic-di-AMP pool: regulation of diadenylate cyclase activity in bacteria
Publisher: Springer Science and Business Media LLC
Date: 13-04-2016
DOI: 10.1007/S00294-016-0600-8
Abstract: Bacteria can sense environmental cues and alter their physiology accordingly through the use of signal transduction pathways involving second messenger nucleotides. One broadly conserved second messenger is cyclic-di-AMP (c-di-AMP) which regulates a range of processes including cell wall homeostasis, potassium uptake, DNA repair, fatty acid synthesis, biofilm formation and central metabolism in bacteria. The intracellular pool of c-di-AMP is maintained by the activities of diadenylate cyclase (DAC) and phosphodiesterase (PDE) enzymes, as well as possibly via c-di-AMP export. Whilst extracellular stimuli regulating c-di-AMP levels in bacteria are poorly understood, recent work has identified effector proteins which directly interact and alter the activity of DACs. These include the membrane bound CdaR and the phosphoglucosamine mutase GlmM which both bind directly to the membrane bound CdaA DAC and the recombination protein RadA which binds directly to the DNA binding DisA DAC. The genes encoding these multiprotein complexes are co-localised in many bacteria providing further support for their functional connection. The roles of GlmM in peptidoglycan synthesis and RadA in Holliday junction intermediate processing suggest that c-di-AMP synthesis by DACs will be responsive to these cellular activities. In addition to these modulatory interactions, permanent dysregulation of DAC activity due to suppressor mutations can occur during selection to overcome growth defects, rapid cell lysis and osmosensitivity. DACs have also been investigated as targets for the development of new antibiotics and several small compound inhibitors have recently been identified. This review aims to provide an overview of how c-di-AMP synthesis by DACs can be regulated.
Effects of a Lactobacillus reuteri BR11 Mutant Deficient in the Cystine-Transport System in a Rat Model of Inflammatory Bowel Disease
Publisher: Springer Science and Business Media LLC
Date: 26-10-2011
DOI: 10.1007/S10620-011-1943-0
Abstract: Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract associated with altered composition of the gut microbiota. Lactobacillus reuteri BR11 (BR11) has recently been reported to reduce the severity of experimental IBD because of its probiotic properties possibly attributed to a mechanism of thiol production via its unique cysteine/cystine-transport system. We compared BR11 and a BR11 mutant deficient in the cystine-uptake system (PNG201), for their capacity to reduce the severity of experimental colitis. Male Sprague-Dawley rats (n = 8 per group) were gavaged (1 ml/day) with skim milk, BR11 or PNG201 (1 × 10(9) CFU/ml) for 12 days. Rats consumed either water or 2% dextran sulfate sodium in drinking water from days 6 to 12 to induce colitis. Metabolism data, disease activity index, intestinal mucin profile, and histological analyses were assessed and compared by ANOVA. Assessed histologically, DSS administration resulted in significant colonic deterioration, including loss of crypt area and increased damage severity. BR11 administration only partially alleviated the DSS effects, with a minor improvement in crypt area (P 0.05) against the DSS control for any of the end-points. However, the mutant strain induced significantly greater (P < 0.05) histological severity compared with BR11-treated colitic animals, indicative of possible exacerbation of colitis. The cystine-uptake system only minimally affects the biological effects of BR11, as evidenced by histological and macroscopic colitic changes.
Modelling of Thermal Sterilisation of High-Moisture Snack Foods: Feasibility Analysis and Optimization
Publisher: Springer Science and Business Media LLC
Date: 08-02-2018
Synergistic antimicrobial activity of galangal (Alpinia galanga), rosemary (Rosmarinus officinalis) and lemon iron bark (Eucalyptus staigerana) extracts
Publisher: Wiley
Date: 28-10-2010
DOI: 10.1002/JSFA.4206
Abstract: In this study the synergistic antimicrobial activities of combinations of extracts from galangal (Alpinia galanga), rosemary (Rosmarinus officinalis) and lemon iron bark (Eucalyptus staigerana) were evaluated against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium and Clostridium perfringens. Chemical compositions of these extracts were also determined to provide further insight into antimicrobial constituents and their potential mechanisms of action. Combinations of galangal with either rosemary or lemon iron bark showed synergistic antimicrobial activity. Specifically, galangal and rosemary showed synergistic activity against S. aureus and L. monocytogenes only, while galangal and lemon iron bark showed synergistic activity against E. coli and S. typhimurium. Chemical compositions of the extracts were determined by gas chromatographic-mass spectrometric analysis. The major chemical components of the galangal and lemon iron bark extracts were 1'-acetoxy-chavicol acetate (1'ACA) (63.4%) and neral (15.6%), respectively, while 1,8-cineole (26.3%) and c hor (20.3%) were identified as major chemical components of the rosemary extract. The results of this study show that galangal, rosemary and lemon iron bark extracts contain components that may have different modes of antimicrobial action and combinations of these extracts may have potential as natural antimicrobials to preserve foods.
Role of Attachment to Surfaces on the Prevalence and Survival of Campylobacter through Food Systems
Publisher: Elsevier BV
Date: 2012
DOI: 10.4315/0362-028X.JFP-11-012
Abstract: C ylobacter continues to be one of the bacterial pathogens most frequently associated with human gastrointestinal illness worldwide. Because C ylobacter primarily colonizes the intestines of animals used for food production, food products of animal origin can become contaminated with this pathogen and thus represent a significant risk factor. Despite application of numerous physical and chemical interventions to control C ylobacter during food processing, the high isolation rate of this pathogen from some retail meat products indicates that C ylobacter is able to persist from animal slaughterhouses through food systems. Given the fastidious growth requirements and high susceptibility of this pathogen to environmental conditions, the ability of C ylobacter to attach to food and food-related surfaces is likely to play an important role in food contamination and movement through food systems. This review was compiled to (i) describe how the attachment of C ylobacter to surfaces influences the prevalence and survival of the organism through food systems, (ii) examine the potential factors affecting the ability of C ylobacter to attach to surfaces, and (iii) suggest strategies for controlling this attachment process.
Future probiotic foods
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/MA20017
Abstract: Foods containing edible probiotic bacteria, most commonly Lactobacillus and Bifidobacterium species, form a multi-billion-dollar industry worldwide. Currently marketed foods containing probiotics are mostly dairy based with yoghurts and fermented milks dominating the industry. Alternative foods as carriers of probiotics are being examined to reduce or eliminate lactose intolerance issues. Food categories including fruit juices, cheese, chocolate and even beer have been shown to be suitable for probiotic delivery. In addition, technologies such as encapsulation in food-grade alginate gels have allowed for improved probiotic survival in certain foodstuffs. We have explored the use of ready-to-eat vegetables such as baby spinach as carriers for commercial probiotics and found that high dose (& log CFU/g) can be achieved without having negative effects on appearance, taste or aroma. Leafy greens as well as other foods and beverages may be suitable probiotic containing new food products in the future.
Lactiplantibacillus plantarum as an adjunct culture exhibits antifungal activity in shredded Cheddar cheese
Publisher: Elsevier BV
Date: 02-2023
Analysis of promoter sequences from Lactobacillus and Lactococcus and their activity in several Lactobacillus species
Publisher: Springer Science and Business Media LLC
Date: 06-04-2000
Abstract: Promoter-active fragments were isolated from the genome of the probiotic organism Lactobacillus rhamnosus strain GG using the promoter-probe vector pNZ272. These promoter elements, together with a promoter fragment isolated from the vaginal strain Lactobacillus fermentum BR11 and two previously defined promoters (Lactococcus lactis and Lactobacillus acidophilus ATCC 4356 slpA), were introduced into three strains of Lactobacillus. Primer-extension analysis was used to map the transcriptional start site for each promoter. All promoter fragments tested were functional in each of the three lactobacilli and a purine residue was used to initiate transcription in most cases. The promoter elements encompassed a 52- to 1,140-fold range in promoter activity depending on the host strain. Lactobacillus promoters were further examined by surveying previously mapped sequences for conserved base positions. The Lactobacillus hexamer regions (-35: TTgaca and -10: TAtAAT) closely resembled those of Escherichia coli and Bacillus subtilis, with the highest degree of agreement at the -10 hexamer. The TG dinucleotide upstream of the -10 hexamer was conserved in 26% of Lactobacillus promoters studied, but conservation rates differed between species. The region upstream of the -35 hexamer of Lactobacillus promoters showed conservation with the bacterial UP element.
Peptide Surface Display and Secretion Using Two LPXTG-Containing Surface Proteins from Lactobacillus fermentum BR11
Publisher: American Society for Microbiology
Date: 03-2005
Influence of cell surface hydrophobicity on attachment of Campylobacter to abiotic surfaces
Publisher: Elsevier BV
Date: 08-2011
Abstract: This work aimed to investigate the influence of physicochemical properties and prior mode of growth (planktonic or sessile culture) on attachment of 13 C ylobacter jejuni strains and 5 C ylobacter coli strains isolated from chicken s les to three abiotic surfaces: stainless steel, glass and polyurethane. Water contact angle and zeta potential measurements indicated that the strains varied with respect to surface hydrophobicity (17.6 ± 1.5 to 53.0 ± 2.3°) and surface charge (-3.3 ± 0.4 to -15.1 ± 0.5 mV). In idual strains had different attachment abilities to stainless steel and glass (3.79 ± 0.16 to 5.45 ± 0.08 log cell cm(-2)) but did not attach to polyurethane, with one exception. Attachment of C ylobacter to abiotic surfaces significantly correlated with cell surface hydrophobicity (P ≤ 0.007), but not with surface charge (P ≥ 0.507). Cells grown as planktonic and sessile culture generally differed significantly from each other with respect to hydrophobicity and attachment (P 0.05). Principal component analysis (PCA) clustered strains into three groups (planktonic culture) and two groups (sessile culture) representing those with similar hydrophobicity and attachment. Of the four highly hydrophobic and adherent strains, three were C. coli suggesting that isolates with greater hydrophobicity and adherence may occur more frequently among C. coli than C. jejuni strains although this requires further investigation using a larger number of strains. Assignment of pulsed-field gel electrophoresis profiles to PCA groups using Jackknife analysis revealed no overall relationship between bacterial genotypes and bacterial attachment. No relationship between serotype distribution and bacterial attachment was apparent in this study.
Isolation of lactic acid bacteria with antifungal activity against the common cheese spoilage mould Penicillium commune and their potential as biopreservatives in cheese
Publisher: Elsevier BV
Date: 12-2014
Solution Structure of the PAS Domain of a Thermophilic YybT Protein Homolog Reveals a Potential Ligand-binding Site
Publisher: Elsevier BV
Date: 04-2013
The Viability of Lactobacillus rhamnosus GG and Lactobacillus acidophilus NCFM Following Double Encapsulation in Alginate and Maltodextrin
Publisher: Springer Science and Business Media LLC
Date: 25-07-2013
Genotyping of dairy Bacillus licheniformis isolates by high resolution melt analysis of multiple variable number tandem repeat loci
Publisher: Elsevier BV
Date: 06-2013
Abstract: In dairy foods, the sporeformer Bacillus licheniformis can be the cause of spoilage or specification compliance issues. Currently used methods for genotyping B. licheniformis have limited discrimination with only 2 or 3 different subgroups being identified. Here, we have developed a multi-locus variable number tandem repeat analysis (MLVA) method and combined it with high resolution melt analysis (MLV-HRMA) for genotyping B. licheniformis. Five repetitive loci were identified and used as markers for genotyping 52 isolates from two milk powder processing plants and retail s les. Nineteen genotypes could be identified using both MLVA and MLV-HRMA leading to Hunter-Gaston discrimination indices (D-value) of 0.93 each. It was found that all 5 MLVA loci were stable following 10 days of sub-culturing of 8 representative isolates. All isolates were also genotyped using previously used methods including randomly lified polymorphic DNA-PCR (RAPD) and partial rpoB sequencing. Five different RAPD profiles and 5 different partial rpoB sequence types were identified resulting in corresponding D-values of 0.6 and 0.46, respectively. Analysis of the genotypes from dairy s les revealed that dairy B. licheniformis isolates are more heterogeneous than previously thought and that this new method can potentially allow for more discriminatory tracking and monitoring of specific genotypes.
Identification and Characterization of the Novel LysM Domain-Containing Surface Protein Sep from Lactobacillus fermentum BR11 and Its Use as a Peptide Fusion Partner in
Publisher: American Society for Microbiology
Date: 06-2004
DOI: 10.1128/AEM.70.6.3673-3680.2004
Abstract: Examination of supernatant fractions from broth cultures of Lactobacillus fermentum BR11 revealed the presence of a number of proteins, including a 27-kDa protein termed Sep. The amino-terminal sequence of Sep was determined, and the gene encoding it was cloned and sequenced. Sep is a 205-amino-acid protein and contains a 30-amino-acid secretion signal and has overall homology (between 39 and 92% identity) with similarly sized proteins of Lactobacillus reuteri , Enterococcus faecium , Streptococcus pneumoniae , Streptococcus agalactiae , and Lactobacillus plantarum . The carboxy-terminal 81 amino acids of Sep also have strong homology (86% identity) to the carboxy termini of the aggregation-promoting factor (APF) surface proteins of Lactobacillus gasseri and Lactobacillus johnsonii . The mature amino terminus of Sep contains a putative peptidoglycan-binding LysM domain, thereby making it distinct from APF proteins. We have identified a common motif within LysM domains that is shared with carbohydrate binding YG motifs which are found in streptococcal glucan-binding proteins and glucosyltransferases. Sep was investigated as a heterologous peptide expression vector in L. fermentum , Lactobacillus rhamnosus GG and Lactococcus lactis MG1363. Modified Sep containing an amino-terminal six-histidine epitope was found associated with the cells but was largely present in the supernatant in the L. fermentum , L. rhamnosus , and L. lactis hosts. Sep as well as the previously described surface protein BspA were used to express and secrete in L. fermentum or L. rhamnosus a fragment of human E-cadherin, which contains the receptor region for Listeria monocytogenes . This study demonstrates that Sep has potential for heterologous protein expression and export in lactic acid bacteria.
Osmoregulation via Cyclic di-AMP signaling
Publisher: Springer International Publishing
Date: 2020
Cystathionine γ-Lyase Is a Component of Cystine-Mediated Oxidative Defense in Lactobacillus reuteri BR11
Publisher: American Society for Microbiology
Date: 15-03-2009
DOI: 10.1128/JB.01553-08
Abstract: Lactobacillus reuteri BR11 possesses a novel mechanism of oxidative defense involving an abundant cystine ABC transporter encoded by the cyuABC gene cluster. Large amounts of thiols, including H 2 S, are secreted upon cystine uptake by the CyuC transporter. A cystathionine γ-lyase ( cgl ) gene is cotranscribed with the cyu genes in several L. reuteri strains and was hypothesized to participate in cystine-mediated oxidative defense by producing reducing equivalents. This hypothesis was tested with L. reuteri BR11 by constructing a cgl mutant (PNG901) and comparing it to a similarly constructed cyuC mutant (PNG902). Although Cgl was required for H 2 S production from cystine, it was not crucial for oxidative defense in de Mann-Rogosa-Sharpe medium, in contrast to CyuC, whose inactivation resulted in lag-phase arrest in aerated cultures. The importance of Cgl in oxidative defense was seen only in the presence of hemin, which poses severe oxidative stress. The growth defects in aerated cultures of both mutants were alleviated by supplementation with cysteine (and cystine in the cgl mutant) but not methionine, with the cyuC mutant showing a much higher concentration requirement. We conclude that L. reuteri BR11 requires a high concentration of exogenous cysteine/cystine to grow optimally under aerobic conditions. This requirement is fulfilled by the abundant CyuC transporter, which has probably arisen due to the broad substrate specificity of Cgl, resulting in a futile pathway which degrades cystine taken up by the CyuC transporter to H 2 S. Cgl plays a secondary role in oxidative defense by its well-documented function of cysteine biosynthesis.
Effect of Antimicrobial Spice and Herb Extract Combinations on Listeria monocytogenes, Staphylococcus aureus, and Spoilage Microflora Growth on Cooked Ready-to-Eat Vacuum-Packaged Shrimp
Publisher: Elsevier BV
Date: 07-2011
Inhibition of bacterial growth in sweet cheese whey by carbon dioxide as determined by culture-independent community profiling
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.IJFOODMICRO.2015.10.003
Abstract: Whey is a valuable co-product from cheese making that serves as a raw material for a wide range of products. Its rich nutritional content lends itself to rapid spoilage, thus it typically needs to be pasteurised and refrigerated promptly. Despite the extensive literature on milk spoilage bacteria, little is known about the spoilage bacteria of whey. The utility of carbon dioxide (CO2) to extend the shelf-life of raw milk and cottage cheese has been well established, but its application in whey preservation has not yet been explored. This study aims to characterise the microbial populations of fresh and spoiled sweet whey by culture-independent community profiling using 454 pyrosequencing of 16S rRNA gene licons and to determine whether carbonation is effective in inhibiting bacterial growth in sweet whey. The microbiota of raw Cheddar and Mozzarella whey was dominated by cheese starter bacteria. After pasteurisation, two out of the three s les studied became dominated by erse environmental bacteria from various phyla, with Proteobacteria being the most dominant. Diverse microbial profiles were maintained until spoilage occurred, when the entire population was dominated by just one or two genera. Whey spoilage bacteria were found to be similar to those of milk. Pasteurised Cheddar and Mozzarella whey was spoiled by Bacillus sp. or Pseudomonas sp., and raw Mozzarella whey was spoiled by Pseudomonas sp., Serratia sp., and other members of the Enterobacteriaceae family. CO2 was effective in inhibiting bacterial growth of pasteurised Cheddar and Mozzarella whey stored at 15°C and raw Mozzarella whey stored at 4°C. The spoilage bacteria of the carbonated s les were similar to those of the non-carbonated controls.
Antimicrobial activity of lysostaphin and a Listeria monocytogenes bacteriophage endolysin produced and secreted by lactic acid bacteria
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.SYAPM.2006.01.013
Abstract: The expression and secretion signals of the Sep protein from Lactobacillus fermentum BR11 were used to direct export of two peptidoglycan hydrolases by Lb. fermentum BR11, Lactobacillus rhamnosus GG, Lactobacillus plantarum ATCC 14917 and Lactococcus lactis MG1363. The production levels, hydrolytic and bacteriocidal activities of the Listeria monocytogenes bacteriophage N-acetylmuramoyl-l-alanine amidase endolysin Ply511 and the glycylglycine endopeptidase lysostaphin were examined. Buffering of the growth media to a neutral pH allowed detection of Ply511 and lysostaphin peptidoglycan hydrolytic activity from all lactic acid bacteria. It was found that purified Ply511 has a pH activity range similar to that of lysostaphin with both enzymes functioning optimally under alkaline conditions. Supernatants from lactobacilli expressing lysostaphin reduced viability of methicillin resistant Staphylococcus aureus (MRSA) by approximately 8 log(10) CFU/ml compared to controls. However, supernatants containing Ply511 were unable to control L. monocytogenes growth. In coculture experiments, both Lb. plantarum and Lb. fermentum synthesizing lysostaphin were able to effectively reduce MRSA cell numbers by >7.4 and 1.7 log(10)CFU/ml, respectively, while lactic acid bacteria secreting Ply511 were unable to significantly inhibit the growth of L. monocytogenes. Our results demonstrate that lysostaphin and Ply511 can be expressed in an active form from different lactic acid bacteria and lysostaphin showed superior killing activity. Lactobacilli producing lysostaphin may have potential for in situ biopreservation in foodstuffs or for prevention of S. aureus infections.
Draft genome sequence of Pseudomonas fluorescens SRM1, an isolate from spoiled raw milk
Publisher: American Society for Microbiology
Date: 30-04-2016
Abstract: Pseudomonas fluorescens is considered a major milk spoilage organism due to its psychrotrophic nature and ability to produce heat-stable proteases and lipases. Here, we report the draft genome and annotation of P. fluorescens SRM1 isolated from spoiled raw milk and the presence of an operon encoding spoilage enzymes.
Rapid identification of dairy mesophilic and thermophilic sporeforming bacteria using DNA high resolution melt analysis of variable 16S rDNA regions
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.IJFOODMICRO.2013.05.007
Abstract: Due to their ubiquity in the environment and ability to survive heating processes, sporeforming bacteria are commonly found in foods. This can lead to product spoilage if spores are present in sufficient numbers and where storage conditions favour spore germination and growth. A rapid method to identify the major aerobic sporeforming groups in dairy products, including Bacillus licheniformis group, Bacillus subtilis group, Bacillus pumilus group, Bacillus megaterium, Bacillus cereus group, Geobacillus species and Anoxybacillus flavithermus was devised. This method involves real-time PCR and high resolution melt analysis (HRMA) of V3 (~70 bp) and V6 (~100 bp) variable regions in the 16S rDNA. Comparisons of HRMA curves from 194 isolates of the above listed sporeforming bacteria obtained from dairy products which were identified using partial 16S rDNA sequencing, allowed the establishment of criteria for differentiating them from each other and several non-sporeforming bacteria found in s les. A blinded validation trial on 28 bacterial isolates demonstrated complete accuracy in unambiguous identification of the 7 different aerobic sporeformers. The reliability of HRMA method was also verified using boiled extractions of crude DNA, thereby shortening the time needed for identification. The HRMA method described in this study provides a new and rapid approach to identify the dominant mesophilic and thermophilic aerobic sporeforming bacteria found in a wide variety of dairy products.
Inactivation of an Iron Transporter in Lactococcus lactis Results in Resistance to Tellurite and Oxidative Stress
Publisher: American Society for Microbiology
Date: 10-2007
DOI: 10.1128/AEM.00413-07
Abstract: In Lactococcus lactis , the interactions between oxidative defense, metal metabolism, and respiratory metabolism are not fully understood. To provide an insight into these processes, we isolated and characterized mutants of L. lactis resistant to the oxidizing agent tellurite (TeO 3 2− ), which generates superoxide radicals intracellularly. A collection of tellurite-resistant mutants was obtained using random transposon mutagenesis of L. lactis . These contained insertions in genes encoding a proton-coupled Mn 2+ /Fe 2+ transport homolog ( mntH ), the high-affinity phosphate transport system ( pstABCDEF ), a putative osmoprotectant uptake system ( choQ ), and a homolog of the oxidative defense regulator spx ( trmA ). The tellurite-resistant mutants all had better survival than the wild type following aerated growth. The mntH mutant was found to be impaired in Fe 2+ uptake, suggesting that MntH is a Fe 2+ transporter in L. lactis . This mutant is capable of carrying out respiration but does not generate as high a final pH and does not exhibit the long lag phase in the presence of hemin and oxygen that is characteristic of wild-type L. lactis . This study suggests that tellurite-resistant mutants also have increased resistance to oxidative stress and that intracellular Fe 2+ can heighten tellurite and oxygen toxicity.
Influence of emulsion droplet size on antimicrobial properties
Publisher: Springer Science and Business Media LLC
Date: 06-2011
Diffusion loading and drug delivery characteristics of alginate gel microparticles produced by a novel impinging aerosols method
Publisher: Informa UK Limited
Date: 19-10-2010
Genetic Characterization of Listeria monocytogenes Isolates from Food Processing Facilities before and after Postcook Chiller Heat Treatment
Publisher: Elsevier BV
Date: 08-2013
Hypervariable pili and flagella genes provide suitable new targets for DNA high-resolution melt-based genotyping of dairy Geobacillus spp.
Publisher: Elsevier BV
Date: 10-2014
Role of Capsular Polysaccharides and Lipooligosaccharides in Campylobacter Surface Properties, Autoagglutination, and Attachment to Abiotic Surfaces
Publisher: Mary Ann Liebert Inc
Date: 06-2013
Abstract: The role of capsular polysaccharides and lipooligosaccharides in cell surface hydrophobicity, surface charge, autoagglutination (AAG), and attachment to abiotic surfaces of three strains of C ylobacter jejuni and one strain of C. coli were investigated. This was achieved by removal of capsular polysaccharides and truncation of lipooligosaccharides core oligosaccharides by inactivation of the kpsE and waaF genes, respectively. The mutants and the wild-type strains were compared after growth under planktonic (broth) and sessile (agar) conditions. Cells grown as planktonic cultures showed a significantly (p 0.05) differences between the three C. jejuni strains and their ΔkpsE and ΔwaaF mutants with respect to all traits tested. Inactivation of the kpsE gene significantly (p<0.05) reduced the surface charge of the C. coli strain from ∼-10 to ∼-6 mV and increased its AAG activity, while disruption of the waaF gene significantly (p 8° and decreased the numbers of cells attaching to stainless steel and glass by ∼0.5 log/cm². These results suggest that surface polysaccharides may influence the surface properties and attachment to abiotic surfaces of C. coli but not C. jejuni. This suggestion, however, requires further investigation using a larger number of strains of both species.
Encapsulation of Lactobacillus plantarum in porous maize starch
Publisher: Elsevier BV
Date: 12-2016
The Characterization of Modified Starch Branching Enzymes: Toward the Control of Starch Chain-Length Distributions
Publisher: Public Library of Science (PLoS)
Date: 13-04-2015
In vitro antimicrobial activity of less-utilized spice and herb extracts against selected food-borne bacteria
Publisher: Elsevier BV
Date: 10-2010
Evaluation of polycaprolactone matrices for the intravaginal delivery of metronidazole in the treatment of bacterial vaginosis
Publisher: SAGE Publications
Date: 28-03-2014
Abstract: Microporous, poly (ɛ-caprolactone) (PCL) matrices loaded with the antibacterial, metronidazole were produced by rapidly cooling suspensions of drug powder in PCL solutions in acetone. Drug incorporation in the matrices increased from 2.0% to 10.6% w/w on raising the drug loading of the PCL solution from 5% to 20% w/w measured with respect to the PCL content. Drug loading efficiencies of 40–53% were obtained. Rapid ‘burst release’ of 35–55% of the metronidazole content was recorded over 24 h when matrices were immersed in simulated vaginal fluid (SVF), due to the presence of large amounts of drug on matrix surface as revealed by Raman microscopy. Gradual release of around 80% of the drug content occurred over the following 12 days. Metronidazole released from PCL matrices in SVF retained antimicrobial activity against Gardnerella vaginalis in vitro at levels up to 97% compared to the free drug. Basic modelling predicted that the concentrations of metronidazole released into vaginal fluid in vivo from a PCL matrix in the form of an intravaginal ring would exceed the minimum inhibitory concentration of metronidazole against G. vaginalis. These findings recommend further investigation of PCL matrices as intravaginal devices for controlled delivery of metronidazole in the treatment and prevention of bacterial vaginosis.
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