ORCID Profile
0000-0002-4732-9175
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)
Wastewater Treatment Processes | Environmental Technologies | Chemical Engineering | Wastewater treatment processes | Environmental Biotechnology not elsewhere classified | Animal protection (incl. pests and pathogens) | Veterinary bacteriology | Environmental Engineering | Environmental biotechnology not elsewhere classified | Pollution and contamination not elsewhere classified | Microbiology | Nanotoxicology, Health and Safety | Microbial Ecology | Pollution and contamination | Chemical engineering | Nanotechnology | Environmental Management | Industrial microbiology (incl. biofeedstocks) | Microbial ecology | Water Treatment Processes | Environmental Nanotechnology | Microbial taxonomy
ANZSRC Socio-Economic Objective (SEO)
Urban and Industrial Water Management | Environmental Health | Ecosystem Assessment and Management of Urban and Industrial Environments | Control of Pests, Diseases and Exotic Species in Urban and Industrial Environments | Climate and Climate Change not elsewhere classified | Management of Liquid Waste from Commercial Services and Tourism (excl. Water) |
Related Links
Publications
Artificial sweeteners stimulate horizontal transfer of extracellular antibiotic resistance genes through natural transformation
Publisher: Springer Science and Business Media LLC
Date: 09-2021
DOI: 10.1038/S41396-021-01095-6
Abstract: Antimicrobial resistance has emerged as a global threat to human health. Natural transformation is an important pathway for horizontal gene transfer, which facilitates the dissemination of antibiotic resistance genes (ARGs) among bacteria. Although it is suspected that artificial sweeteners could exert antimicrobial effects, little is known whether artificial sweeteners would also affect horizontal transfer of ARGs via transformation. Here we demonstrate that four commonly used artificial sweeteners (saccharin, sucralose, aspartame, and acesulfame potassium) promote transfer of ARGs via natural transformation in Acinetobacter baylyi ADP1, a model organism for studying competence and transformation. Such phenomenon was also found in a Gram-positive human pathogen Bacillus subtilis and mice faecal microbiome. We reveal that exposure to these sweeteners increases cell envelope permeability and results in an upregulation of genes encoding DNA uptake and translocation (Com) machinery. In addition, we find that artificial sweeteners induce an increase in plasmid persistence in transformants. We propose a mathematical model established to predict the long-term effects on transformation dynamics under exposure to these sweeteners. Collectively, our findings offer insights into natural transformation promoted by artificial sweeteners and highlight the need to evaluate these environmental contaminants for their antibiotic-like side effects.
Advanced nitrogen removal using pilot-scale SBR with intelligent control system built on three layer network
Publisher: Springer Science and Business Media LLC
Date: 02-2007
Disinfection spreads antimicrobial resistance
Publisher: American Association for the Advancement of Science (AAAS)
Date: 29-01-2021
Chlorine disinfection facilitates natural transformation through ROS-mediated oxidative stress
Publisher: Springer Science and Business Media LLC
Date: 03-05-2021
DOI: 10.1038/S41396-021-00980-4
Abstract: The bacterial infection that involves antimicrobial resistance is a rising global threat to public health. Chlorine-based water disinfection processes can inactivate antibiotic resistant bacteria. However, at the same time, these processes may cause the release of antibiotic resistance genes into the water as free DNA, and consequently increase the risk to disseminate antibiotic resistance via natural transformation. Presently, little is known about the contribution of residual chlorine affecting the transformation of extracellular antibiotic resistance genes (ARGs). This study investigates whether chloramine and free chlorine promote the transformation of ARGs and how this may occur. We reveal that both chloramine and free chlorine, at practically relevant concentrations, significantly stimulated the transformation of plasmid-encoded ARGs by the recipient Acinetobacter baylyi ADP1, by up to a 10-fold increase. The underlying mechanisms underpinning the increased transformations were revealed. Disinfectant exposure induced a series of cell responses, including increased levels of reactive oxygen species (ROS), bacterial membrane damage, ROS-mediated DNA damage, and increased stress response. These effects thus culminated in the enhanced transformation of ARGs. This promoted transformation was observed when exposing disinfectant-pretreated A. baylyi to free plasmid. In contrast, after pretreating free plasmid with disinfectants, the transformation of ARGs decreased due to the damage of plasmid integrity. These findings provide important insight on the roles of disinfectants affecting the horizontal transfer of ARGs, which could be crucial in the management of antibiotic resistance in our water systems.
Growth kinetics of Candidatus ‘Methanoperedens nitroreducens’ enriched in a laboratory reactor
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.SCITOTENV.2018.12.351
Abstract: Recently it has been shown that Candidatus 'Methanoperedens nitroreducens', an anaerobic methanotrophic archaea (ANME), can reduce nitrate to nitrite using electrons derived from anaerobic oxidation of methane. In this study, the growth kinetics of 'M. nitroreducens' enriched in a laboratory reactor were studied. In the experimental concentration range (up to 16 mg CH
Unraveling microbial structure and diversity of activated sludge in a full-scale simultaneous nitrogen and phosphorus removal plant using metagenomic sequencing.
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.ENZMICTEC.2017.03.009
Abstract: Activated sludge contains highly complex microbial communities, which play crucial roles in pollutant removal performance in wastewater treatment plants (WWTPs). Metagenomic sequencing was applied to characterize microbial community and functional profiles within activated sludge from a full-scale municipal WWTP carrying out simultaneous nitrogen and phosphorous removal (SNPR). We applied the assembled contigs (N90 of 591bp) and predicted genes to conduct taxonomic and function annotations, respectively. Results revealed the extraordinary microbial ersity of activated sludge, which included detection of minority populations that are difficult to be explored by traditional molecular methods. Taxonomic analysis indicated that the dominant bacterial phyla were Proteobacteria, Nitrospirae, Bacteroidetes, Actinobacteria and Firmicutes. The abundance of the key organisms involved in nitrogen and phosphorous removal were qualified. Aerobic ammonia-oxidizing bacteria distinctly dominate over ammonia-oxidizing archaea and anaerobic ammonium oxidation bacteria. Various key enzymes involved in the global nitrogen cycle were annotated in the activated sludge. High abundance of the known polyphosphate accumulating organisms was detected (approximately 4.89% of the overall population reads), supporting good phosphorous removal performance. This study provides a comprehensive insight into the community structure and ersity of the SNPR system, and will provide foundation for optimal operation of nutrient removal systems.
Cross-feeding interactions in short chain gaseous alkane-driven perchlorate and selenate reduction
Publisher: Elsevier BV
Date: 07-2021
Pathways and Organisms Involved in Ammonia Oxidation and Nitrous Oxide Emission
Publisher: Informa UK Limited
Date: 2013
Novel Multiplexed Amplicon-Based Sequencing to Quantify SARS-CoV-2 RNA from Wastewater
Publisher: American Chemical Society (ACS)
Date: 08-07-2021
Metagenomic analysis reveals wastewater treatment plants as hotspots of antibiotic resistance genes and mobile genetic elements
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.WATRES.2017.07.002
Abstract: The intensive use of antibiotics results in their continuous release into the environment and the subsequent widespread occurrence of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs). This study used Illumina high-throughput sequencing to investigate the broad-spectrum profiles of both ARGs and MGEs in activated sludge and anaerobically digested sludge from a full-scale wastewater treatment plant. A pipeline for identifying antibiotic resistance determinants was developed that consisted of four categories: gene transfer potential, ARG potential, ARGs pathway and ARGs phylogenetic origin. The metagenomic analysis showed that the activated sludge and the digested sludge exhibited different microbial communities and changes in the types and occurrence of ARGs and MGEs. In total, 42 ARGs subtypes were identified in the activated sludge, while 51 ARG subtypes were detected in the digested sludge. Additionally, MGEs including plasmids, transposons, integrons (intI1) and insertion sequences (e.g. ISSsp4, ISMsa21 and ISMba16) were abundant in the two sludge s les. The co-occurrence pattern between ARGs and microbial taxa revealed by network analysis indicated that some environmental bacteria (e.g. Clostridium and Nitrosomonas) might be potential hosts of multiple ARGs. The findings increase our understanding of WWTPs as hotspots of ARGs and MGEs, and contribute towards preventing their release into the downstream environment.
Spatiotemporal heterogeneity of core functional bacteria and their synergetic and competitive interactions in denitrifying sulfur conversion-assisted enhanced biological phosphorus removal
Publisher: Springer Science and Business Media LLC
Date: 07-09-2017
DOI: 10.1038/S41598-017-11448-X
Abstract: Denitrifying sulfur conversion-assisted enhanced biological phosphorus removal (DS-EBPR) has recently been developed for simultaneously removing nitrogen and phosphorus from saline sewage with minimal sludge production. This novel process could potentially enable sustainable wastewater treatment. Yet, the core functional bacteria and their roles are unknown. Here, we used high-throughput 16S rRNA gene sequencing coupled with principal coordinates analysis and ANOVA with Tukey’s test to unravel the spatiotemporal heterogeneity of functional bacteria and their synergetic and competitive interactions. We did not find any obvious spatial heterogeneity within the bacterial population in different size-fractionated sludge s les, but the main functional bacteria varied significantly with operation time. Thauera was enriched (9.26~13.63%) as become the core functional genus in the DS-EBPR reactors and links denitrifying phosphorus removal to sulfide oxidation. The other two functional genera were sulfate-reducing Desulfobacter (4.31~12.85%) and nitrate-reducing and sulfide-oxidizing Thiobacillus (4.79~9.92%). These bacteria cooperated in the DS-EBPR process: Desulfobacter reduced sulfate to sulfide for utilization by Thiobacillus , w hile Thauera and Thiobacillus competed for nitrate and sulfide as well as Thauera and Desulfobacter competed for acetate. This study is the first to unravel the interactions among core functional bacteria in DS-EBPR, thus improving our understanding of how this removal process works.
Filamentous and non-filamentous bulking of activated sludge encountered under nutrients limitation or deficiency conditions
Publisher: Elsevier BV
Date: 11-2014
Nitrite Oxidation in Wastewater Treatment: Microbial Adaptation and Suppression Challenges
Publisher: American Chemical Society (ACS)
Date: 17-08-2023
Effects of Light Energy with Different Densities on Denitrification: Metabolic Intermediates, Electron Behavior, Enzyme Activities, and Sludge Settleability
Publisher: American Chemical Society (ACS)
Date: 12-01-2023
Non-antibiotic antimicrobial triclosan induces multiple antibiotic resistance through genetic mutation
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.ENVINT.2018.06.004
Abstract: Antibiotic resistance poses a major threat to public health. Overuse and misuse of antibiotics are generally recognized as the key factors contributing to antibiotic resistance. However, whether non-antibiotic, anti-microbial (NAAM) chemicals can directly induce antibiotic resistance is unclear. We aim to investigate whether the exposure to a NAAM chemical triclosan (TCS) has an impact on inducing antibiotic resistance on Escherichia coli. Here, we report that at a concentration of 0.2 mg/L TCS induces multi-drug resistance in wild-type Escherichia coli after 30-day TCS exposure. The oxidative stress induced by TCS caused genetic mutations in genes such as fabI, frdD, marR, acrR and soxR, and subsequent up-regulation of the transcription of genes encoding beta-lactamases and multi-drug efflux pumps, together with down-regulation of genes related to membrane permeability. The findings advance our understanding of the potential role of NAAM chemicals in the dissemination of antibiotic resistance in microbes, and highlight the need for controlling biocide applications.
Efficient photocatalytic destruction of recalcitrant micropollutants using graphitic carbon nitride under simulated sunlight irradiation
Publisher: Elsevier BV
Date: 2021
Inhibition of methanogens decreased sulfadiazine removal and increased antibiotic resistance gene development in microbial fuel cells
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.BIORTECH.2019.02.089
Abstract: The aim of this work was to study sulfadiazine (SDZ) biodegradation efficiency, antibiotic resistance genes (ARGs) development and shift of microbial communities under conditions of limited methanogens activity in Microbial fuel cells (MFCs). The results indicated that the removal performance of SDZ was decreased with the suppression of methanogens in both MFCs and open-circuit controls. The relative abundances of ARGs were even enhanced by the inhibition of methanogens. The biodegradation mechanism of SDZ was obtained, in which SDZ was initially ided into aniline and pyrimidin-2ylsulfamic acid, then converted into small molecules. Geobacter was found as the dominant microorganism, indicating its potential to degrade SDZ in the MFCs. These findings suggest there is a trade-off between electricity production and SDZ removal and ARG development by the mean of methanogen inhibition in MFCs.
Hot spring distribution and survival mechanisms of thermophilic comammox Nitrospira
Publisher: Springer Science and Business Media LLC
Date: 17-04-2023
DOI: 10.1038/S41396-023-01409-W
Abstract: The recent discovery of Nitrospira species capable of complete ammonia oxidation (comammox) in non-marine natural and engineered ecosystems under mesothermal conditions has changed our understanding of microbial nitrification. However, little is known about the occurrence of comammox bacteria or their ability to survive in moderately thermal and/or hyperthermal habitats. Here, we report the wide distribution of comammox Nitrospira in five terrestrial hot springs at temperatures ranging from 36 to 80°C and provide metagenome-assembled genomes of 11 new comammox strains. Interestingly, the identification of dissimilatory nitrate reduction to ammonium (DNRA) in thermophilic comammox Nitrospira lineages suggests that they have versatile ecological functions as both sinks and sources of ammonia, in contrast to the described mesophilic comammox lineages, which lack the DNRA pathway. Furthermore, the in situ expression of key genes associated with nitrogen metabolism, thermal adaptation, and oxidative stress confirmed their ability to survive in the studied hot springs and their contribution to nitrification in these environments. Additionally, the smaller genome size and higher GC content, less polar and more charged amino acids in usage profiles, and the expression of a large number of heat shock proteins compared to mesophilic comammox strains presumably confer tolerance to thermal stress. These novel insights into the occurrence, metabolic activity, and adaptation of comammox Nitrospira in thermal habitats further expand our understanding of the global distribution of comammox Nitrospira and have significant implications for how these unique microorganisms have evolved thermal tolerance strategies.
Effective and robust partial nitrification to nitrite by real-time aeration duration control in an SBR treating domestic wastewater
Publisher: Elsevier BV
Date: 09-2009
Mitigation of antibiotic resistance in a pilot-scale system treating wastewater from high-speed railway trains
Publisher: Elsevier BV
Date: 04-2020
DOI: 10.1016/J.CHEMOSPHERE.2019.125484
Abstract: Wastewater from high-speed railway trains represents a mobile reservoir of microorganisms with antibiotic resistance. It harbors abundant and erse antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). This study investigated the removal of ARB and ARGs in a pilot-scale reactor, which consisted of an anaerobic/anoxic/oxic process, anaerobic/anoxic/aerobic process, and ozone-based disinfection to treat 1 m
CHAPTER 16. Denitrification Processes for Wastewater Treatment
Publisher: Royal Society of Chemistry
Date: 2016
Microbial Methane Conversion to Short-Chain Fatty Acids Using Various Electron Acceptors in Membrane Biofilm Reactors.
Publisher: American Chemical Society (ACS)
Date: 08-10-2019
Abstract: Given our vast methane reserves and the forecasted shortage of crude oil in the not too distant future, the conversion of methane into value-added liquid chemicals or fuels would be beneficial. The generated chemicals or fuels could augment the petroleum-dominated chemical market, and also satisfy the increasing demand for transportation fuels. While methane bioconversion to liquid chemicals has just been reported recently, there is limited understanding of the process. This study aims to clarify the potential electron acceptors that could support the process. Here we operated four membrane biofilm reactors (MBfRs) fed with nitrate, nitrite, oxygen at a relatively low rate, and oxygen at a relatively high rate, respectively, to study if they can support methane bioconversion to short-chain fatty acids (SCFAs) and the associated microbiological features. All tested electron acceptors facilitated methane bioconversion to SCFAs (ranging from 1.1 to 36.7 mg acetate L
Development and Experimental Evaluation of a Steady-state Model for the Step-feed Biological Nitrogen Removal Process
Publisher: Elsevier BV
Date: 06-2007
Efficient nitrogen removal from mainstream wastewater through coupling Partial Nitritation, Anammox and Methane-dependent nitrite/nitrate reduction (PNAM)
Publisher: Elsevier BV
Date: 11-2021
Sulfur-based Mixotrophic Vanadium (V) Bio-reduction towards Lower Organic Requirement and Sulfate Accumulation
Publisher: Elsevier BV
Date: 02-2021
Versatility of nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO): First demonstration with real wastewater
Publisher: Elsevier BV
Date: 04-2021
Evaluating the Role of Microbial Internal Storage Turnover on Nitrous Oxide Accumulation During Denitrification.
Publisher: Springer Science and Business Media LLC
Date: 14-10-2015
DOI: 10.1038/SREP15138
Abstract: Biological wastewater treatment processes under a dynamic regime with respect to carbon substrate can result in microbial storage of internal polymers (e.g., polyhydroxybutyrate (PHB)) and their subsequent utilizations. These storage turnovers play important roles in nitrous oxide (N 2 O) accumulation during heterotrophic denitrification in biological wastewater treatment. In this work, a mathematical model is developed to evaluate the key role of PHB storage turnovers on N 2 O accumulation during denitrification for the first time, aiming to establish the key relationship between N 2 O accumulation and PHB storage production. The model is successfully calibrated and validated using N 2 O data from two independent experimental systems with PHB storage turnovers. The model satisfactorily describes nitrogen reductions, PHB storage/utilization and N 2 O accumulation from both systems. The results reveal a linear relationship between N 2 O accumulation and PHB production, suggesting a substantial effect of PHB storage on N 2 O accumulation during denitrification. Application of the model to simulate long-term operations of a denitrifying sequencing batch reactor and a denitrifying continuous system indicates the feeding pattern and sludge retention time would alter PHB turnovers and thus affect N 2 O accumulation. Increasing PHB utilization could substantially raise N 2 O accumulation due to the relatively low N 2 O reduction rate when using PHB as carbon source.
Microbial Perchlorate Reduction Driven by Ethane and Propane
Publisher: American Chemical Society (ACS)
Date: 12-01-2021
Efficient nitrate removal from synthetic groundwater via in situ utilization of short-chain fatty acids from methane bioconversion
Publisher: Elsevier BV
Date: 08-2020
Comparison of performance, microorganism populations, and bio-physiochemical properties of granular and flocculent sludge from denitrifying phosphorus removal reactors
Publisher: Elsevier BV
Date: 02-2015
Toxicity Assessment of Nano-ZnO Exposure on the Human Intestinal Microbiome, Metabolic Functions, and Resistome Using an In Vitro Colon Simulator
Publisher: American Chemical Society (ACS)
Date: 10-05-2021
Selective enrichment and metagenomic analysis of three novel comammox Nitrospira in a urine-fed membrane bioreactor
Publisher: Springer Science and Business Media LLC
Date: 25-03-2021
DOI: 10.1038/S43705-021-00005-3
Abstract: The discovery of complete ammonia-oxidizing (comammox) Nitrospira has added an important new process to the microbial nitrogen cycle. While comammox Nitrospira have been detected in various ecosystems, only few studies have achieved their enrichment over other canonical nitrifiers. Here, we obtained a selective enrichment of comammox Nitrospira in a urine-fed membrane bioreactor in less than 200 days. By using 16S rRNA gene licon sequencing and quantitative PCR of the functional marker gene amoA , we observed a dominance (up to 30% relative abundance) of comammox Nitrospira over ammonia-oxidizing bacteria and archaea. Furthermore, the complete genomes of three new clade A comammox Nitrospira were recovered by metagenomics. These three strains were ergent from previously reported comammox species according to comparative genome and amoA -based analyses. In addition to the key genes for ammonia and nitrite oxidation, the three recovered genomes contained a complete urea utilization pathway. Our findings suggest that the urea present in the urine media played a significant role in the selective enrichment of these novel comammox Nitrospira , and support the ersity and versatility of their metabolism.
Biological Removal of Nitrogen from Wastewater
Publisher: Springer New York
Date: 2008
DOI: 10.1007/978-0-387-71724-1_5
Abstract: This comprehensive review discusses erse conventional and novel technologies for nitrogen removal from wastewater. Novel technologies have distinct advantages in terms of saving configuration, aeration, and carbon sources. Each novel technology possesses promising features and potential problems. For instance, SND and OLAND processes can achieve 100% total nitrogen removal, but the low oxygen concentration required by these two processes substantially reduces the nitrification rate, which limits their application. On the other hand, denitrification can still be carried out by aerobic denitrifiers at high DO levels in activated sludge process, but it is difficult to cultivate this type of bacteria. The SHARON process is most commonly used for shortcut nitrification and denitrification because of its low requirements for retention time, oxygen concentration, and carbon source. However, its high operational temperature (about 35 degrees C) limits the application. Several real-time control strategies (DO, pH, and ORP) have been developed to achieve a stable nitrite accumulation in SHARON. The ANAMMOX process can sustain at high total-N loadings and has been employed in full-scale treatment plants, but the problem of nitrite supply has not been solved, and the treated wastewater still contains nitrate. In addition, the inoculation and enrichment of ANAMMOX bacteria (i.e., anaerobic AOB) is difficult. The problem of nitrite supply has been solved by combining partial nitrification with ANAMMOX, which provides abundant nitrite for anaerobic AOB. ANAMMOX is currently used for treating sludge digestion supernatant. Aerobic dammonitrification is a process combining partial nitrification and ANAMMOX at different layers of biofilm. Although the technology has been tested in pilot- and full-scale experiments, the mechanism is still unclear. CANON and OLAND are one-step ammonium removal processes that possess distinct advantages of saving carbon sources and aeration costs. The major challenge is the enrichment of anaerobic microorganisms capable of oxidizing ammonia with nitrite as the electron acceptor. Molecular biology and environmental biotechnology can help identify functional microorganisms, characterize microbial communities, and develop new nitrogen removal processes. Extensive research should be conducted to apply and optimize these novel processes in wastewater treatment plants. More effort should be invested to combine these novel processes (e.g., partial nitrification, ANAMMOX) to enhance nitrogen removal efficiency.
A new approach to simultaneous ammonium and dissolved methane removal from anaerobic digestion liquor: A model-based investigation of feasibility
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.WATRES.2015.08.046
Abstract: The presence of a high level of dissolved methane (e.g., 20-26 g m(-3)) in the anaerobic sludge digestion liquor represents a major challenge to the treatment of this stream, as its emission to the atmosphere contributes significantly to the carbon footprint of wastewater treatment. Here we propose a new approach to simultaneous ammonium and dissolved methane removal from the anaerobic digestion liquor through integrating partial nitritation-Anammox and denitrifying anaerobic methane oxidation (DAMO) processes in a single-stage membrane biofilm reactor (MBfR). In such an MBfR, the anaerobic digestion liquor is provided in the bulk liquid, while oxygen is supplied through gas-permeable membranes to avoid dissolved methane stripping. A previously developed model with appropriate extensions was applied to assess the system performance under different operational conditions and the corresponding microbial interactions. Both influent surface loading (or hydraulic retention time) and oxygen surface loading are found to significantly influence the total nitrogen (TN) and dissolved methane removal, which jointly determine the overall system performance. The counter diffusion and concentration gradients of substrates cause microbial stratification in the biofilm, where ammonia-oxidizing bacteria (AOB) attach close to the membrane surface (biofilm base) where oxygen and ammonium are available, while Anammox and DAMO microorganisms jointly grow in the biofilm layer close to the bulk liquid where methane, ammonium, and nitrite are available with the latter produced by AOB. These results provide first insights and useful information for the design and operation of this new technology for simultaneous ammonium and dissolved methane removal in its potential future applications.
Long-term impact of anaerobic reaction time on the performance and granular characteristics of granular denitrifying biological phosphorus removal systems
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.WATRES.2013.06.013
Abstract: Removal of nitrogen and phosphorus (P) from wastewater is successfully and widely practiced in systems employing both granular sludge technology and enhanced biological P removal (EBPR) processes however, the key parameter, anaerobic reaction time (AnRT), has not been thoroughly investigated. Successful EBPR is highly dependent on an appropriate AnRT, which induces carbon and polyphosphate metabolism by phosphorus accumulating organisms (PAOs). Therefore, the long-term impact of AnRT on denitrifying P removal performance and granular characteristics was investigated in three identical granular sludge sequencing batch reactors with AnRTs of 90 (R1), 120 (R2) and 150 min (R3). The microbial community structures and anaerobic stoichiometric parameters related to various AnRTs were monitored over time. Free nitrite acid (FNA) accumulation (e.g., 0.0008-0.0016 mg HNO2-N/L) occurred frequently owing to incomplete denitrification in the adaptation period, especially in R3, which influenced the anaerobic/anoxic intracellular intermediate metabolites and activities of intracellular enzymes negatively, resulting in lower levels of poly-P and reduced activity of polyphosphate kinase. As a result, the Accumulibacter-PAOs population decreased from 51 ± 2.5% to 43 ± 2.1% when AnRT was extended from 90 to 150 min, leading to decreased denitrifying P removal performance. Additionally, frequent exposure of microorganisms to the FNA accumulation and anaerobic endogenous conditions in excess AnRT cases (e.g., 150 min) stimulated increased extracellular polymeric substances (EPS) production by microorganisms, resulting in enhanced granular formation and larger granules (size of 0.6-1.2 mm), but decreasing anaerobic PHA synthesis and glycogen hydrolysis. Phosphorus removal capacity was mediated to some extent by EPS adsorption in granular sludge systems that possessed more EPS, longer AnRT and relatively higher GAOs.
Changes in the microbial community structure of filaments and floc formers in response to various carbon sources and feeding patterns
Publisher: Springer Science and Business Media LLC
Date: 21-05-2014
DOI: 10.1007/S00253-014-5805-5
Abstract: Filamentous bulking is a complicated problem in wastewater treatment plants treating various wastewaters, leading to the deterioration of the settling properties and the effluent quality. This study systematically investigated long-term effects of various carbon sources and feeding patterns on the growth of filamentous bacteria, in order to reveal the mechanism of filamentous bulking. Sludge volume index (SVI), microscopic observations, staining (Gram and Neisser staining), scan electron microscopic, and fluorescent in situ hybridization (FISH) were used to monitor the bulking and track the changes of microbial morphology and community structure of activated sludge in six lab-scale sequencing batch reactors (SBRs) fed with different carbon sources. Filamentous bulking was not observed in all SBRs under anoxic feeding pattern with a short fill time, in which SVI remained below 150 mL/g. In contrast, serious bulking (SVI > 500 mL/g) occurred under aerobic feeding pattern when fed with ethanol, propionate, acetate, and glucose, in which Thiothrix and Sphaerotilus natans proliferated as dominant filaments. Compared to glucose-fed reactor, relatively light bulking was caused in starch-fed reactor with the growth of Nostocoida limicola II. In addition, flocs in starch-fed reactor were more open and fluffy than flocs formed on readily biodegradable substrates. Finally, a framework integrating kinetic selection, diffusion selection, storage selection, and protozoa capture mechanism was proposed to explain filamentous bulking.
Transcriptomics Uncovers the Response of Anammox Bacteria to Dissolved Oxygen Inhibition and the Subsequent Recovery Mechanism
Publisher: American Chemical Society (ACS)
Date: 04-11-2020
Different clusters of Candidatus ‘Methanoperedens nitroreducens’-like archaea as revealed by high-throughput sequencing with new primers
Publisher: Springer Science and Business Media LLC
Date: 16-05-2018
DOI: 10.1038/S41598-018-24974-Z
Abstract: The newly discovered Candidatus ‘Methanoperedens nitroreducens’ ( M . nitroreducens ), mediating nitrate-dependent anaerobic oxidation of methane, is an important microorganism in linking carbon and nitrogen cycles. In order to explore the ersity of M . nitroreducens -like archaea in various environmental niches with advanced high-throughput sequencing, new primers based on alpha subunit of methyl-coenzyme M reductase gene were designed. The PCR results demonstrated that the new primers could effectively detect M . nitroreducens -like archaea from an enrichment culture dominated by M . nitroreducens as well as s les collected from a natural freshwater lake and a full-scale wastewater treatment plant (WWTP). By high-throughput sequencing, more than 30,000 M . nitroreducens -like sequences were obtained. Phylogenetic analysis of these sequences along with published sequences showed that M . nitroreducens -like archaea could be ided into three sub-branches (named as Group A, Group B and Group C in this study). Clear geographical difference was observed, with Group A and Group B dominating s les in Queensland (Australia) and in European ecosystems, respectively. Further quantitative PCR revealed that the M . nitroreducens -like archaea were more abundant in WWTP than the freshwater lake. The study provided a large number of sequences for M . nitroreducens -like archaeal communities, thus expanded our understanding on the ecological ersity of M . nitroreducens -like archaea.
Achieving nitrite accumulation in a continuous system treating low-strength domestic wastewater: switchover from batch start-up to continuous operation with process control
Publisher: Springer Science and Business Media LLC
Date: 18-11-2011
DOI: 10.1007/S00253-011-3702-8
Abstract: Although biological nitrogen removal via nitrite is recognized as one of the cost-effective and sustainable biological nitrogen removal processes, nitrite accumulation has proven difficult to achieve in continuous processes treating low-strength nitrogenous wastewater. Partial nitrification to nitrite was achieved and maintained in a lab-scale completely stirred tank reactor (CSTR) treating real domestic wastewater. During the start-up period, sludge with ammonia-oxidizing bacteria (AOB) but no nitrite-oxidizing bacteria (NOB) was obtained by batch operation with aeration time control. The nitrifying sludge with the dominance of AOB was then directly switched into continuous operation. It was demonstrated that partial nitrification to nitrite in the continuous system could be repeatedly and reliably achieved using this start-up strategy. The ratio of dissolved oxygen to ammonium loading rate (DO/ALR) was critical to maintain high ammonium removal efficiency and nitrite accumulation ratio. Over 85% of nitrite accumulation ratio and more than 95% of ammonium removal efficiency were achieved at DO/ALR ratios in an optimal range of 4.0-6.0 mg O(2)/g N d, even under the disturbances of ammonium loading rate. Microbial population shift was investigated, and fluorescence in situ hybridization analysis indicated that AOB were the dominant nitrifying bacteria over NOB when stable partial nitrification was established.
Characterization of the dissolved organic matter in sewage effluent of sequence batch reactor: the impact of carbon source
Publisher: Springer Science and Business Media LLC
Date: 30-06-2011
Stable limited filamentous bulking through keeping the competition between floc-formers and filaments in balance
Publisher: Elsevier BV
Date: 2012
DOI: 10.1016/J.BIORTECH.2011.08.114
Abstract: Limited filamentous bulking (LFB) was proposed to save aeration energy consumption and enhance the capacity of filaments to degrade substrates with low concentrations in activated sludge systems. Operational parameters favorable for maintaining the LFB state were investigated in an anoxic-oxic reactor treating domestic wastewater. The experiments showed that the LFB state would deteriorate with sharply decreasing temperature, reducing substrate gradients or removing anoxic zones. The balance between filaments and floc-formers could be achieved by controlling dissolved oxygen and sludge loading rates to be in optimal ranges. Eikelboom Type 0041 and CandidatusMicrothrix parvicella were the filamentous bacteria responsible for the LFB state. However, the excess growth of Eikelboom Type 021N and Sphaerotilus natans were observed when serious bulking occurred under low substrate gradients. It was demonstrated that stable maintenance of LFB for energy saving was feasible by process control and optimization.
rDNA- and rRNA-derived communities present divergent assemblage patterns and functional traits throughout full-scale landfill leachate treatment process trains
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.SCITOTENV.2018.07.388
Abstract: Understanding the influences of microbial interactions and niche heterogeneities on microbial communities and functional traits is critical for determining its engineering and ecological significance. However, little is known about microbial community assemblage and functional gene expression throughout full-scale landfill leachate treatment plants. Here, we applied a combination of 16S rRNA and rDNA licon sequencing, shotgun metagenomic, and qPCR approaches to unveil the ecological associations between distinct communities, functional gene expression and nitrogen cycling processes. By comparing the rDNA and rRNA-derived communities, the rRNA/rDNA ratios suggested that 57.2% of rare taxa were active, and their abundance decreased as increasing of potential activities. In particular, rDNA- and rRNA-based communities exhibited ergent assemblage patterns, and stronger intra-associations among core taxa in the rRNA-based communities than in rDNA-based communities. Furthermore, results regarding both bacterial assemblage and functional traits indicated that the habitat filtering and niche differentiation (treatment units) exerted selection on microbial communities based on functional traits, particular for key ecological functions related to nitrogen cycling. Collectively, our findings provide insights into structure-function associations at the local level and shed light on ecological rules guiding rDNA- and rRNA-based community assembly in landfill leachate treatment systems.
Silver Nanoparticles Entering Soils via the Wastewater–Sludge–Soil Pathway Pose Low Risk to Plants but Elevated Cl Concentrations Increase Ag Bioavailability
Publisher: American Chemical Society (ACS)
Date: 15-07-2016
Abstract: The widespread use of silver nanoparticles (Ag-NPs) results in their movement into wastewater treatment facilities and subsequently to agricultural soils via application of contaminated sludge. On-route, the chemical properties of Ag may change, and further alterations are possible upon entry to soil. In the present study, we examined the long-term stability and (bio)availability of Ag along the "wastewater-sludge-soil" pathway. Synchrotron-based X-ray absorption spectroscopy (XAS) revealed that ca. 99% of Ag added to the sludge reactors as either Ag-NPs or AgNO3 was retained in sludge, with ≥79% of this being transformed to Ag2S, with the majority (≥87%) remaining in this form even after introduction to soils at various pH values and Cl concentrations for up to 400 days. Diffusive gradients in thin films (DGT), chemical extraction, and plant uptake experiments indicated that the potential (bio)availability of Ag in soil was low but increased markedly in soils with elevated Cl, likely due to the formation of soluble AgClx complexes in the soil solution. Although high Cl concentrations increased the bioavailability of Ag markedly, plant growth was not reduced in any treatment. Our results indicate that Ag-NPs entering soils through the wastewater-sludge-soil pathway pose low risk to plants due to their conversion to Ag2S in the wastewater treatment process, although bioavailability may increase in saline soils or when irrigated with high-Cl water.
Feasibility of methane bioconversion to methanol by acid-tolerant ammonia-oxidizing bacteria
Publisher: Elsevier BV
Date: 06-2021
Simultaneous removal of antibiotic resistant bacteria, antibiotic resistance genes, and micropollutants by a modified photo-Fenton process
Publisher: Elsevier BV
Date: 06-2021
Larger Anammox Granules not only Harbor Higher Species Diversity but also Support More Functional Diversity
Publisher: American Chemical Society (ACS)
Date: 29-10-2020
Nitrate reduction by denitrifying anaerobic methane oxidizing microorganisms can reach a practically useful rate
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.WATRES.2015.09.026
Abstract: Methane in biogas has been proposed to be an electron donor to facilitate complete nitrogen removal using denitrifying anaerobic methane oxidizing (DAMO) microorganisms in an anaerobic ammonium oxidation (anammox) reactor, by reducing the nitrate produced. However, the slow growth and the low activity of DAMO microorganisms cast a serious doubt about the practical usefulness of such a process. In this study, a previously established lab-scale membrane biofilm reactor (MBfR), with biofilms consisting of a coculture of DAMO and anammox microorganisms, was operated to answer if the DAMO reactor can achieve a nitrate reduction rate that can potentially be applied for wastewater treatment. Through progressively increasing nitrate and ammonium loading rates to the reactor, a nitrate removal rate of 684 ± 10 mg-N L(-1) d(-1) was achieved after 453 days of operation. This rate is, to our knowledge, by far the highest reported for DAMO reactors, and far exceeds what is predicted to be required for nitrate removal in a sidestream (5.6-135 mg-N L(-1) d(-1)) or mainstream anammox reactor (3.2-124 mg-N L(-1) d(-1)). Mass balance analysis showed that the nitrite produced by nitrate reduction was jointly reduced by anammox bacteria at a rate of 354 ± 3 mg-N L(-1) d(-1), accompanied by an ammonium removal rate of 268 ± 2 mg-N L(-1) d(-1), and DAMO bacteria at a rate of 330 ± 9 mg-N L(-1) d(-1). This study shows that the nitrate reduction rate achieved by the DAMO process can be high enough for removing nitrate produced by anammox process, which would enable complete nitrogen removal from wastewater.
Data on metagenomic profiles of activated sludge from a full-scale wastewater treatment plant
Publisher: Elsevier BV
Date: 12-2017
Island biogeography on a micro-scale: Larger anammox granules not only harbor higher species diversity but also support more functional diversity
Publisher: Research Square Platform LLC
Date: 25-03-2020
DOI: 10.21203/RS.3.RS-18517/V1
Abstract: Background: According to the theory of island biogeography, there is a strong relationship between the species ersity and the isolated area. However, it is unclear whether the ecological distribution of microorganisms follows this island biogeography pattern at micro-scale. Here, we use microbial granules harvested from a partial nitritation and anammox (PN/A) system as a model to test if the microbial and functional ersity follow the island biogeography. We collected and ided these granules into five discrete size-fractions ( .2, 0.2–0.5, 0.5–0.8, 0.8–1.0 and .0 mm). Results: By comparing the composition and functional attribute of five pools of the size-fractionated granules by 16S rRNA gene licon, metagenomic and metatranscriptomic sequencing, larger granules were shown not only to harbor higher microbial ersity, but also to support more erse functions than smaller granules. De novo co-assembly and binning of metagenomic reads yielded 22 near-complete genomes of dominant microorganisms, which allowed us to infer an ecological model of the microbial ecosystem in anammox-based granules. This genome-based ecological model indicates that nitrifying organisms in smaller granules feed nitrite to anammox bacteria in larger granules. Conclusion: Our findings substantiate that microbial communities in PN/A granules follow a species-volume relationship, suggesting the generality of the theory of island biogeography on microscopic scale.
Biological sludge reduction and enhanced nutrient removal in a pilot-scale system with 2-step sludge alkaline fermentation and A2O process
Publisher: Elsevier BV
Date: 03-2011
DOI: 10.1016/J.BIORTECH.2010.12.051
Abstract: To enhance nutrient removal performance and reduce disposal amount of waste activated sludge (WAS), a pilot-scale continuous system consisting of a 2-step sludge alkaline fermentation process and an A(2)O reactor was proposed. The feasibility of WAS reducing and resourcing by alkaline fermentation was investigated. Volatile fatty acids (VFA) yield was higher under alkaline condition than that under acidic condition. Through 2-step alkaline fermentation, substantial VFA was accumulated, and then elutriated out continuously from an up-flow column by domestic wastewater. The results showed that 38.2% of sludge was hydrolyzed, 19.7% was finally acidified into VFA, and as high as 42.1% of WAS was reduced. Moreover, after introducing the fermentation liquids with higher proportion of acetic acid and propionic acid into the A(2)O reactor, the total nitrogen and phosphorus removal efficiencies reached to 80.1% and 90.0%, respectively. Sludge reduction and enhanced nutrient removal could be achieved simultaneously in the proposed system.
Spatial distribution of dynamics characteristic in the intermittent aeration static composting of sewage sludge
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.BIORTECH.2011.01.083
Abstract: Spatial differences and temporal changes in biological activity characteristics were investigated in a static reactor using intermittent aeration during the sewage sludge composting process. Pumice was proposed as a bulking agent in the composting of sewage sludge. Variations in temperature, moisture, oxygen level, volatile solids, specific oxygen uptake rate (SOUR) and dehydrogenase activity (DHA) were determined during 28 days of composting. The peak temperature in the upper region of the reactor was 10°C higher than that at the bottom. The moisture level in the middle region was significantly higher than that of other positions. Analysis of SOUR and DHA indicated that the lowest level of sludge stability was at the bottom region. These spatial and temporal differences in biochemical dynamics in the static system could extend the composting period and affect product uniformity.
Phylogenetic and metabolic diversity of microbial communities performing anaerobic ammonium and methane oxidations under different nitrogen loadings
Publisher: Springer Science and Business Media LLC
Date: 25-04-2023
DOI: 10.1038/S43705-023-00246-4
Abstract: The microbial guild coupling anammox and nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) is an innovative process to achieve energy-efficient nitrogen removal with the beneficial use of methane in biogas or in anaerobically treated wastewater. Here, metagenomics and metatranscriptomics were used to reveal the microbial ecology of two biofilm systems, which incorporate anammox and n-DAMO for high-level nitrogen removal in low-strength domestic sewage and high-strength sidestream wastewater, respectively. We find that different nitrogen loadings (i.e., 0.1 vs. 1.0 kg N/m 3 /d) lead to different combinations of anammox bacteria and anaerobic methanotrophs (“ Candidatus Methanoperedens” and “ Candidatus Methylomirabilis”), which play primary roles for carbon and nitrogen transformations therein. Despite methane being the only exogenous organic carbon supplied, heterotrophic populations (e.g., Verrucomicrobiota and Bacteroidota) co-exist and actively perform partial denitrification or dissimilatory nitrate reduction to ammonium (DNRA), likely using organic intermediates from the breakdown of methane and biomass as carbon sources. More importantly, two novel genomes belonging to “ Ca . Methylomirabilis” are recovered, while one surprisingly expresses nitrate reductases, which we designate as “ Ca . Methylomirabilis nitratireducens” representing its inferred capability in performing nitrate-dependent anaerobic methane oxidation. This finding not only suggests a previously neglected possibility of “ Ca . Methylomirabilis” bacteria in performing methane-dependent nitrate reduction, and also challenges the previous understanding that the methane-dependent complete denitrification from nitrate to dinitrogen gas is carried out by the consortium of bacteria and archaea.
High-Rate Production of Short-Chain Fatty Acids from Methane in a Mixed-Culture Membrane Biofilm Reactor
Publisher: American Chemical Society (ACS)
Date: 19-10-2018
Non-antibiotic pharmaceuticals enhance the transmission of exogenous antibiotic resistance genes through bacterial transformation
Publisher: Springer Science and Business Media LLC
Date: 18-05-2020
DOI: 10.1038/S41396-020-0679-2
Abstract: Antibiotic resistance is a serious global threat for public health. Considering the high abundance of cell-free DNA encoding antibiotic resistance genes (ARGs) in both clinical and environmental settings, natural transformation is an important horizontal gene transfer pathway to transmit antibiotic resistance. It is acknowledged that antibiotics are key drivers for disseminating antibiotic resistance, yet the contributions of non-antibiotic pharmaceuticals on transformation of ARGs are overlooked. In this study, we report that some commonly consumed non-antibiotic pharmaceuticals, at clinically and environmentally relevant concentrations, significantly facilitated the spread of antibiotic resistance through the uptake of exogenous ARGs. This included nonsteroidal anti-inflammatories, ibuprofen, naproxen, diclofenac, the lipid-lowering drug, gemfibrozil, and the β-blocker propranolol. Based on the results of flow cytometry, whole-genome RNA sequencing and proteomic analysis, the enhanced transformation of ARGs was affiliated with promoted bacterial competence, enhanced stress levels, over-produced reactive oxygen species and increased cell membrane permeability. In addition, a mathematical model was proposed and calibrated to predict the dynamics of transformation during exposure to non-antibiotic pharmaceuticals. Given the high consumption of non-antibiotic pharmaceuticals, these findings reveal new concerns regarding antibiotic resistance dissemination exacerbated by non-antibiotic pharmaceuticals.
A comparative proteomic analysis of Desulfovibrio vulgaris Hildenborough in response to the antimicrobial agent free nitrous acid
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.SCITOTENV.2019.03.442
Abstract: Sulfate reducing bacteria (SRB) can contribute to facilitating serious concrete corrosion through the production of hydrogen sulfide in sewers. Recently, free nitrous acid (FNA) was discovered as a promising antimicrobial agent to inhibit SRB activities thereby limiting hydrogen sulfide production in sewers. However, knowledge of the bacterial response to increasing levels of the antimicrobial agent is unknown. Here we report the proteomic response of Desulfovibrio vulgaris Hildenborough and reveal that the antimicrobial effect of FNA is multi-targeted and dependent on the FNA levels. This was achieved using a sequential window acquisition of all theoretical mass spectrometry analysis to determine protein abundance variations in D. vulgaris during exposure to different FNA concentrations. When exposed to 1.0 μg N/L FNA, nitrite reduction (nitrite reductase) related proteins and nitrosative stress related proteins, including the hybrid cluster protein, showed distinct increased abundances. When exposed to 4.0 and 8.0 μg N/L FNA, increased abundance was detected for proteins putatively involved in nitrite reduction. Abundance of proteins involved in the sulfate reduction pathway (from adenylylphophosulfate to sulfite) and lactate oxidation pathway (from pyruvate to acetate) were initially inhibited in response to FNA at 8 h incubation, and then recovered at 12 h incubation. Lowered ribosomal protein abundance in D. vulgaris was detected, however, total cellular protein levels were mostly constant in the presence or absence of FNA. In addition, this study indicates that proteins coded by genes DVU2543, DVU0772, and DVU3212 potentially participate in resisting oxidative stress with FNA exposure. These findings share new insights for understanding the dynamic responses of D. vulgaris to FNA and could be useful to guide and improve the practical applications of FNA-based technologies for control of sewer corrosion.
Evaluation of mainstream nitrogen removal by simultaneous partial nitrification, anammox and denitrification (SNAD) process in a granule-based reactor
Publisher: Elsevier BV
Date: 11-2017
Culture-dependent enumeration methods failed to simultaneously detect disinfectant-injured and genetically modified Escherichia coli in drinking water
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6EM00625F
Abstract: A comparison of four culture-dependent enumeration methods for disinfectant-injured and GM E. coli in water.
Non-antibiotic pharmaceuticals promote the transmission of multidrug resistance plasmids through intra- and intergenera conjugation
Publisher: Springer Science and Business Media LLC
Date: 10-03-2021
DOI: 10.1038/S41396-021-00945-7
Abstract: Antibiotic resistance is a global threat to public health. The use of antibiotics at sub-inhibitory concentrations has been recognized as an important factor in disseminating antibiotic resistance via horizontal gene transfer. Although non-antibiotic, human-targeted pharmaceuticals are widely used by society (95% of the pharmaceuticals market), the potential contribution to the spread of antibiotic resistance is not clear. Here, we report that commonly consumed, non-antibiotic pharmaceuticals, including nonsteroidal anti-inflammatories (ibuprofen, naproxen, diclofenac), a lipid-lowering drug (gemfibrozil), and a β -blocker (propranolol), at clinically and environmentally relevant concentrations, significantly accelerated the dissemination of antibiotic resistance via plasmid-borne bacterial conjugation. Various indicators were used to study the bacterial response to these drugs, including monitoring reactive oxygen species (ROS) and cell membrane permeability by flow cytometry, cell arrangement, and whole-genome RNA and protein sequencing. Enhanced conjugation correlated well with increased production of ROS and cell membrane permeability. Additionally, these non-antibiotic pharmaceuticals induced responses similar to those detected when bacteria are exposed to antibiotics, such as inducing the SOS response and enhancing efflux pumps. The findings advance understanding of the transfer of antibiotic resistance genes, emphasizing the concern that non-antibiotic, human-targeted pharmaceuticals enhance the spread of antibiotic resistance among bacterial populations.
Nutrient removal performance and microbial community structure in an EBPR system under the limited filamentous bulking state
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.BIORTECH.2013.06.103
Abstract: Limited filamentous bulking (LFB) was proposed to be a new method for saving energy and improving effluent quality. In order to validate the stability of LFB in enhanced biological phosphorus removal (EBPR) systems, the LFB was further achieved in a lab-scale EBPR. Nutrient removal performance and microbial community structure including dominant filaments and polyphosphate-accumulating organisms (PAOs) were investigated. Results showed that the enriched PAOs could alleviate the negative effect of low dissolved oxygen concentration on sludge settleability, making the LFB be more easily achieved and maintained in the EBPR for long-term operation. Sludge volume index was kept between 150-200 mL/g during the LFB period. Larger floc size (≥400 μm) was commonly observed under the LFB state, which significantly enhanced the simultaneous nitrification and denitrification (SND) efficiency. An average SND efficiency of 36% was observed in the EBPR system when the LFB occurred.
Microbial Chromate Reduction Coupled to Anaerobic Oxidation of Elemental Sulfur or Zerovalent Iron
Publisher: American Chemical Society (ACS)
Date: 18-02-2019
Abstract: Chromate (Cr(VI)), as one of ubiquitous contaminants in groundwater, has posed a major threat to public health and ecological environment. Although various electron donors (e.g., organic carbon, hydrogen, and methane) have been proposed to drive chromate removal from contaminated water, little is known for microbial chromate reduction coupled to elemental sulfur (S(0)) or zerovalent iron (Fe(0)) oxidation. This study demonstrated chromate could be biologically reduced by using S(0) or Fe(0) as inorganic electron donor. After 60-day cultivation, the sludge achieved a high Cr(VI) removal efficiency of 92.9 ± 1.1% and 98.1 ± 1.2% in two independent systems with S(0) or Fe(0) as the sole electron donor, respectively. The deposited Cr(III) was identified as the main reduction product based on X-ray photoelectron spectroscopy. High-throughput 16S rRNA gene sequencing indicated that Cr(VI) reduction coupled to S(0) or Fe(0) oxidation was mediated synergically by a microbial consortia. In such the consortia, S(0)- or Fe(0)-oxidizing bacteria (e.g., Thiobacillus or Ferrovibrio) could generate volatile fatty acids as metabolites, which were further utilized by chromate-reducing bacteria (e.g., Geobacter or Desulfovibrio) to reduce chromate. Our findings advance our understanding on microbial chromate reduction supported by solid electron donors and also offer a promising process for groundwater remediation.
Control filamentous bulking caused by chlorine-resistant Type 021N bacteria through adding a biocide CTAB.
Publisher: Elsevier BV
Date: 12-2012
DOI: 10.1016/J.WATRES.2012.09.037
Abstract: Filamentous bulking sludge due to excessive growth of filamentous bacteria is a serious operational problem in activated sludge plants. The addition of chemicals is one of widespread ways to control filamentous bulking. In this study, filamentous bulking in a continuous activated sludge system was found to be mainly caused by Eikelboom Type 021N filamentous bacteria likely due to low substrate concentration gradients. These Type 021N bacteria were found to be resistant to chlorination, maintaining cell integrity at a dosage of up to 80 mg Cl/gSS. An alternative biocidal agent, cetyltrimethyl ammonium bromide (CTAB), exhibited a much stronger biocidal effect on these filaments, which significantly improved sludge settleability. Type 021N with filamentous index of 5 was selectively killed, but floc-formers recovery their activity after CTAB termination. The study implied that CTAB might have more penetration capacity to cell wall of chlorine-resistant Type 021N bacteria. We therefore suggest the penetration property of filament cell wall should be considered or tested before the selection of biocide type in practice.
Both silver ions and silver nanoparticles facilitate the horizontal transfer of plasmid-mediated antibiotic resistance genes
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.WATRES.2019.115229
Abstract: Antibiotic resistance in bacteria is a growing threat to global human health. Horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs) is recognized as the primary contributor to antibiotic resistance dissemination. Silver nanoparticles (AgNPs) are widely used in personal care products as antimicrobial agents. While heavy metals are known to induce antibiotic resistance in bacteria, it is not known whether AgNPs in the environment can stimulate the HGT of ARGs. Here, we report that both AgNPs and ionic silver Ag
Energy saving achieved by limited filamentous bulking sludge under low dissolved oxygen
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.BIORTECH.2009.09.051
Abstract: Limited filamentous bulking caused by low dissolved oxygen (DO) was proposed to establish a low energy consumption wastewater treatment system. This method for energy saving was derived from two full-scale field observations, which showed pollutants removal would be enhanced and energy consumption could be reduced by at least 10% using limited filamentous bulking. Furthermore, preliminary investigation including the abundance evaluation and the identification of filamentous bacteria demonstrated that the limited filamentous bulking could be repeated steadily in a lab-scale anoxic-oxic reactor fed with domestic wastewater. The sludge loss did not occur in the secondary clarifier, while COD and total nitrogen removal efficiencies were improved by controlling DO for optimal filamentous bacterial population. Suspended solids in effluent were negligible and turbidity was lower than 2 NTU, which were distinctly lower than those under no bulking. Theoretical and experimental results indicated the aeration consumption could be saved by the application of limited filamentous bulking.
Antidepressant fluoxetine induces multiple antibiotics resistance in Escherichia coli via ROS-mediated mutagenesis
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.ENVINT.2018.07.046
Abstract: Antibiotic resistance poses a great threat to global public health. Overuse of antibiotics is generally considered as the major factor contributing to it. However, little is known about whether non-antibiotic drugs could play potential roles in the emergence of antibiotic resistance. We aimed to investigate whether antidepressant fluoxetine induces multiple antibiotic resistances and reveal underlying mechanisms. Escherichia coli K12 was exposed to different concentrations of fluoxetine (0, 0.5, 5, 50 and 100 mg/L) and the resistant strains were isolated by plating on antibiotic containing plates. Resistant strains were randomly selected to determine the increase of minimum inhibition concentration (MIC) of multiple antibiotics. Genome-wide DNA sequencing was performed on cells cultured in lysogeny broth (LB) without any fluoxetine or antibiotics exposure. RNA sequencing and proteomic profiling of isolated mutants grown in LB with 100 mg/L fluoxetine were analyzed to reveal the underlying mechanisms. Exposure of Escherichia coli to fluoxetine at 5-100 mg/L after repeated subculture in LB for 30 days promoted its mutation frequency resulting in increased resistance against the antibiotics chlor henicol, amoxicillin and tetracycline. This increase was up to 5.0 × 10 Our findings for the first time demonstrated that the exposure to antidepressant fluoxetine induces multiple antibiotic resistance in E. coli via the ROS-mediated mutagenesis.
Dissecting microbial community structure and methane-producing pathways of a full-scale anaerobic reactor digesting activated sludge from wastewater treatment by metagenomic sequencing
Publisher: Springer Science and Business Media LLC
Date: 14-03-2015
Antidepressants can induce mutation and enhance persistence toward multiple antibiotics
Publisher: Proceedings of the National Academy of Sciences
Date: 23-01-2023
Abstract: Antibiotic resistance is an urgent threat to global health. Antidepressants are consumed in large quantities, with a similar pharmaceutical market share (4.8%) to antibiotics (5%). While antibiotics are acknowledged as the major driver of increasing antibiotic resistance, little attention is paid to the contribution of antidepressants in this process. Here, we demonstrate that antidepressants at clinically relevant concentrations induce resistance to multiple antibiotics, even following short periods of exposure. Antibiotic persistence was also enhanced. Phenotypic and genotypic analyses revealed the enhanced production of reactive oxygen species following exposure to antidepressants was directly associated with increased resistance. An enhanced stress signature response and stimulation of efflux pump expression were also associated with increased resistance and persistence. Mathematical modeling also predicted that antidepressants would accelerate the emergence of antibiotic-resistant bacteria, and persister cells would help to maintain the resistance. Overall, our findings highlight the antibiotic resistance risk caused by antidepressants.
High abundance and diversity of nitrite-dependent anaerobic methane-oxidizing bacteria in a paddy field profile
Publisher: Oxford University Press (OUP)
Date: 15-09-2014
Abstract: The discovery of nitrite-dependent anaerobic methane oxidation (n-damo) mediated by 'Candidatus Methylomirabilis oxyfera' with nitrite and methane as substrates has connected biogeochemical carbon and nitrogen cycles in a new way. The paddy fields often carry substantial methane and nitrate, thus may be a favorable habitat for n-damo bacteria. In this paper, the vertical-temporal molecular fingerprints of M. oxyfera-like bacteria, including abundance and community composition, were investigated in a paddy soil core in Jiangyin, near the Yangtze River. Through qPCR investigation, high abundance of M. oxyfera-like bacteria up to 1.0 × 10(8) copies (g d.w.s.)(-1) in summer and 8.5 × 10(7) copies (g d.w.s.)(-1) in winter was observed in the ecotone of soil and groundwater in the paddy soil core, which was the highest in natural environments to our knowledge. In the ecotone, the ratio of M. oxyfera-like bacteria to total bacteria reached peak values of 2.80% in summer and 4.41% in winter. Phylogenetic analysis showed n-damo bacteria in the paddy soil were closely related to M. oxyfera and had high ersity in the soil/groundwater ecotone. All of the results indicated the soil/groundwater ecotone of the Jiangyin paddy field was a favorable environment for the growth of n-damo bacteria.
Chlorine disinfection promotes the exchange of antibiotic resistance genes across bacterial genera by natural transformation
Publisher: Springer Science and Business Media LLC
Date: 23-04-2020
DOI: 10.1038/S41396-020-0656-9
Abstract: Chlorine disinfection to drinking water plays an important role in preventing and controlling waterborne disease outbreaks globally. Nevertheless, little is known about why it enriches the antibiotic resistance genes (ARGs) in bacteria after chlorination. Here, ARGs released from killed antibiotic-resistant bacteria (ARB), and culturable chlorine-injured bacteria produced in the chlorination process as the recipient, were investigated to determine their contribution to the horizontal transfer of ARGs during disinfection treatment. We discovered Esch e richia coli , Salmonella aberdeen , Pseudomonas aeruginosa and Enterococcus faecalis showed erse resistance to sodium hypochlorite, and transferable RP4 could be released from killed sensitive donor consistently. Meanwhile, the survival of chlorine-tolerant injured bacteria with enhanced cell membrane permeabilisation and a strong oxidative stress-response demonstrated that a physiologically competent cell could be transferred by RP4 with an improved transformation frequency of up to 550 times compared with the corresponding untreated bacteria. Furthermore, the water quality factors involving chemical oxygen demand (COD Mn ), ammonium nitrogen and metal ions (Ca 2+ and K + ) could significantly promote above transformation frequency of released RP4 into injured E. faecalis . Our findings demonstrated that the chlorination process promoted the horizontal transfer of plasmids by natural transformation, which resulted in the exchange of ARGs across bacterial genera and the emergence of new ARB, as well as the transfer of chlorine-injured opportunistic pathogen from non-ARB to ARB. Considering that the transfer elements were quite resistant to degradation through disinfection, this situation poses a potential risk to public health.
Evidence of differential adaptation to decreased temperature by anammox bacteria
Publisher: Wiley
Date: 13-09-2018
Abstract: Low temperature is recognized as one of the major barriers for the application of the anaerobic ammonium oxidation (anammox) process to treat mainstream wastewater. Studies are yet to reveal the underlying biological limitations and molecular mechanisms associated with the inhibition of low temperature on the anammox process. In this study, metaproteomics was used to examine proteome modulation patterns of the anammox community occurring at different temperatures. The anammox community remarkably altered their proteomes when the temperature decreased from 35 °C to 20 °C. This was especially for proteins involved in energy conversion, transcription and translation and inorganic ion transport. However, at 15 °C the anammox activities became distinctly inhibited, and there was evidence of energy limitations and severe stress in Candidatus Kuenenia and to a lesser degree in Candidatus Brocadia. Candidatus Jettenia exhibited more changes in its proteome at 15 °C. From the proteomes, at the lower temperatures there was evidence of stress caused by toxic nitrogen compounds or reactive oxygen species in the anammox bacteria. Hydroxylamine oxidoreductase (HAO)-like proteins and an oxidative stress response protein (a catalase) were in high abundance to potentially ameliorate these inhibitory effects. This study offers metaproteomic insight into the anammox community-based physiological response to decreasing temperatures.
Synergistic Combination of Graphitic Carbon Nitride and Peroxymonosulfate for Efficient Photocatalytic Destruction of Emerging Contaminants under Simulated Solar Irradiation
Publisher: American Chemical Society (ACS)
Date: 08-12-2023
Theoretical analysis and enhanced nitrogen removal performance of step-feed SBR
Publisher: IWA Publishing
Date: 09-2008
DOI: 10.2166/WST.2008.409
Abstract: To achieve high nitrification and denitrification rates, step-feed SBR with multiple aerobic and anoxic phases was adopted to study nitrogen removal performance. Theoretical analysis of step-feed SBR was presented first, from which feeding steps and C/N ratio had significant influences on nitrogen removal performance. Total nitrogen removal efficiency would increase with increasing of feeding steps, while the increasing extent was not distinct with feeding steps above 4. At a given feeding step, nitrogen removal efficiency would also increase with increasing of C/N ratio. Experimental work was conducted in a lab-scale SBR to investigate practical effects of these critical factors, using real municipal wastewater. The results showed when C/N ratio was appropriately decreasing influent flow mode could achieve enhanced nitrogen removal with less adding of external carbon source, compared with equal influent flow mode. Three-step equal influent flow mode was recommended to treat common municipal wastewater in view of operation complexity. Non steady-state experiments over about three months confirmed step-feed SBR was an enhanced nitrogen removal process with high efficiency. Total nitrogen in the effluent was under 2 mg/L, the average removal efficiency achieved for TN was over 97% just adding a little external carbon source, and good sludge settleability was obtained.
Colonization of gut microbiota by plasmid-carrying bacteria is facilitated by evolutionary adaptation to antibiotic treatment
Publisher: Springer Science and Business Media LLC
Date: 13-12-2021
DOI: 10.1038/S41396-021-01171-X
Abstract: Multidrug-resistant plasmid-carrying bacteria are of particular clinical concern as they could transfer antibiotic resistance genes to other bacterial species. However, little is known whether evolutionary adaptation of plasmid-carrying bacteria after long-term antibiotic exposure could affect their subsequent colonization of the human gut. Herein, we combined a long-term evolutionary model based on Escherichia coli K-12 MG1655 and the multidrug-resistant plasmid RP4 with in vivo colonization experiments in mice. We found that the evolutionary adaptation of plasmid-carrying bacteria to antibiotic exposure facilitated colonization of the murine gut and subsequent plasmid transfer to gut bacteria. The evolved plasmid-carrying bacteria exhibited phenotypic alterations, including multidrug resistance, enhanced bacterial growth and biofilm formation capability and decreased plasmid fitness cost, which might be jointly caused by chromosomal mutations (SNPs in rpoC , proQ , and hcaT ) and transcriptional modifications. The upregulated transcriptional genes, e.g., type 1 fimbrial-protein pilus ( fimA and fimH ) and the surface adhesin gene ( flu ) were likely responsible for the enhanced biofilm-forming capacity. The gene tnaA that encodes a tryptophanase-catalyzing indole formation was transcriptionally upregulated, and increased indole products participated in facilitating the maximum population density of the evolved strains. Furthermore, several chromosomal genes encoding efflux pumps (acriflavine resistance proteins A and B ( acrA, acrB ), outer-membrane protein ( tolC ), multidrug-resistance protein ( mdtM ), and macrolide export proteins A and B ( macA , macB )) were transcriptionally upregulated, while most plasmid-harboring genes (conjugal transfer protein ( traF ) and ( trbB ), replication protein gene ( trfA ), beta-lactamase TEM precursor ( bla TEM ), aminoglycoside 3'-phosphotransferase ( aphA ) and tetracycline resistance protein A ( tetA )) were downregulated. Collectively, these findings demonstrated that evolutionary adaptation of plasmid-carrying bacteria in an antibiotic-influenced environment facilitated colonization of the murine gut by the bacteria and plasmids.
Perchlorate bio-reduction in a methane-based membrane biofilm reactor in the presence and absence of oxygen
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.WATRES.2019.04.008
Abstract: Perchlorate has been widely detected in various water environments and could cause serious health problems. Methane has been proposed as a promising electron donor to remove perchlorate from contaminated water, yet it is unclear whether and how microbial methane oxidation couples with perchlorate reduction, in particular under anoxic conditions. Here, the feasibility and performance of perchlorate reduction driven by methane in the presence and absence of oxygen were investigated and compared in a lab-scale methane-based membrane biofilm reactor. Long-term operational performance suggested that perchlorate was reduced to chloride, with 4 mg Cl/L/d of perchlorate removal rate under anoxic conditions. Differently, perchlorate removal rate increased to 16 mg Cl/L/d, and volatile fatty acids (VFAs) were produced from methane partial oxidation when a limited oxygen (10 mg/L/d) was externally supplied. Regardless of oxygen conditions, microbial perchlorate reduction driven by methane might be mediated through synergistic interactions by a microbial consortium, but with different key microbial members under both oxygen regimes. Under anoxic conditions, aerobic methanotrophs (likely Methylocystaceae and Methylococcaceae) might micro-aerobically oxidize methane by utilizing internal oxygen from microbial perchlorate reduction, which might be mediated by Rhodocyclaceae. In contrast, under oxygen-limiting conditions, methanogens (e.g., Methanosarcina) and fermenters (e.g., Veillonellaceae) likely jointly converted methane into VFAs, then dissimilatory perchlorate-reducing bacteria (e.g., Rhodocyclaceae) utilized the produced VFAs to reduce perchlorate to chloride. Our findings provide evidence to link methane oxidation with perchlorate reduction under both oxygen regimes, which could be facilitated to design a process to remove perchlorate from groundwater.
Effect of short-term light irradiation with varying energy densities on the activities of nitrifiers in wastewater
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.WATRES.2022.118291
Abstract: Microalgal-bacterial consortium (MBC) process has been proposed as an alternative to conventional activated sludge process for nitrogen removal from wastewater. As one of the most influencing parameters, light irradiation effects on microalgae have been extensively investigated. However, light influence on the performance of nitrifiers in activated sludge and its mechanism remains unclear. In this study, the effects of three factors (light irradiation power, irradiation time and sludge concentration) on activities and physiological characteristics of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were systematically studied through both the Design of Experiments driven response surface methodology (RSM) approach and light-nitrification kinetic modeling. Results indicated that light irradiation with the specific light energy density (Es) at 0.0203-0.1571 kJ·mg
Microbial Stratification Affects Conversions of Nitrogen and Methane in Biofilms Coupling Anammox and n-DAMO Processes
Publisher: American Chemical Society (ACS)
Date: 24-02-2023
Biological Bromate Reduction Driven by Methane in a Membrane Biofilm Reactor
Publisher: American Chemical Society (ACS)
Date: 04-12-2017
Biogeographical distribution of denitrifying anaerobic methane oxidizing bacteria in C hinese wetland ecosystems
Publisher: Wiley
Date: 02-12-2014
Abstract: The discovery of denitrifying anaerobic methane oxidation with nitrite as electron acceptor mediated by 'Candidatus Methylomirabilis oxyfera' connected the biogeochemical carbon and nitrogen cycle in a new way. However, it is important to have a comprehensive understanding about the distribution of M. oxyfera-like bacteria in the terrestrial realm, especially the wetland ecosystems that are known as the largest natural source of atmospheric methane. Here, our molecular evidence demonstrated that a wide geographical distribution of M. oxyfera-like bacteria at oxic/anoxic interfaces of various wetlands (n = 91) over the Chinese territory. Intriguingly, the M. oxyfera-like bacteria were detected in some extreme environments, indicating that M. oxyfera-like bacteria occupied a wide range of habitats. Quantitative polymerase chain reaction estimated that the abundance of M. oxyfera-like bacteria ranged from 2.2 × 10(3) to 2.3 × 10(7) copies g(-1) dry soil, and up to around 0.62% of the total number of bacteria. Moreover, the M. oxyfera-like bacteria showed high bio ersity in wetland ecosystems based on the analysis of 462 pmoA and 287 16S rRNA gene sequences. The current study revealed the widespread distribution and biogeography of M. oxyfera-like bacteria in the terrestrial system.
Triclosan at environmental concentrations can enhance the spread of extracellular antibiotic resistance genes through transformation
Publisher: Elsevier BV
Date: 04-2020
Interactions of functional microorganisms and their contributions to methane bioconversion to short-chain fatty acids
Publisher: Elsevier BV
Date: 07-2021
Copper Oxide Nanoparticles Induce Lysogenic Bacteriophage and Metal-Resistance Genes in Pseudomonas aeruginosa PAO1
Publisher: American Chemical Society (ACS)
Date: 30-06-2017
Abstract: The intensive use of metal-based nanoparticles results in their continuous release into the environment, leading to potential risks for human health and microbial ecosystems. Although previous studies have indicated that nanoparticles may be toxic to microorganisms, there is a scarcity of data available to assess the underlying molecular mechanisms of inhibitory and biocidal effects of nanoparticles on microorganisms. This study used physiological experiments, microscopy, live/dead staining, and the genome-wide RNA sequencing to investigate the multiple responses of Pseudomonas aeruginosa to the exposure of copper oxide nanoparticles (CuO NPs). The results for the first time show that CuO NPs induce lysogenic bacteriophage, which might render defective within a bacterial host. The presence of CuO NPs causes nitrite accumulation and great increases in N
Microbial community structure and biodiversity of size-fractionated granules in a partial nitritation-anammox process
Publisher: Oxford University Press (OUP)
Date: 18-02-2017
Abstract: The performance of a granule-based partial nitritation-anammox process is expected to be affected by the granule size distribution, but little is known about the impact of granule size on microbial community structure and ersity. To reveal how the microbial composition and ersity vary with granule size, granules from a partial nitritation-anammox reactor were size-fractionated into five classes ( 1.0 mm). Microbial communities and ersity in these size-fractionated granules were investigated using 16S rRNA gene high-throughput sequencing. It was found that larger granules harbor more erse microbial communities than small granules. Both quantitative PCR and 16S rRNA gene sequencing indicated that the abundance of anammox bacteria (dominated by Candidatus Brocadia) exhibited an increasing trend with granule size. In contrast, the abundance of ammonia-oxidizing bacteria (Nitrosomonas) decreased with increasing granule size. Moreover, larger granules harbored more erse anammox bacteria, with four genera found in the largest granules while only two with limited abundance were detected in the smallest granules. The findings highlight an important role for granule size in shaping community structure and bio ersity.
Autotrophic nitrogen removal in membrane-aerated biofilms: Archaeal ammonia oxidation versus bacterial ammonia oxidation
Publisher: Elsevier BV
Date: 10-2016
Silver nanoparticles stimulate the proliferation of sulfate reducing bacterium Desulfovibrio vulgaris
Publisher: Elsevier BV
Date: 02-2018
DOI: 10.1016/J.WATRES.2017.11.021
Abstract: The intensive use of silver nanoparticles (AgNPs) in cosmetics and textiles causes their release into sewer networks of urban water systems. Although a few studies have investigated antimicrobial activities of nanoparticles against environmental bacteria, little is known about potential impacts of the released AgNPs on sulfate reducing bacteria in sewers. Here, we investigated the effect of AgNPs on Desulfovibrio vulgaris Hidenborough (D. vulgaris), a typical sulfate-reducing bacterium (SRB) in sewer systems. We found AgNPs stimulated the proliferation of D. vulgaris, rather than exerting inhibitory or biocidal effects. Based on flow cytometer detections, both the cell growth rate and the viable cell ratio of D. vulgaris increased during exposure to AgNPs at concentrations of up to 100 mg/L. The growth stimulation was dependent on the AgNP concentration. These results imply that the presence of AgNPs in sewage may affect SRB abundance in sewer networks. Our findings also shed new lights on the interactions of nanoparticles and bacteria.
Rapid formation of granules coupling n-DAMO and anammox microorganisms to remove nitrogen
Publisher: Elsevier BV
Date: 04-2021
Control Strategies to Combat Dissemination of Antibiotic Resistance in Urban Water Systems
Publisher: Springer International Publishing
Date: 2020
DOI: 10.1007/698_2020_474
Methane-supported nitrate removal from groundwater in a membrane biofilm reactor
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.WATRES.2017.12.064
Abstract: The discovery of denitrifying anaerobic methane oxidation (DAMO) has not only improved our understanding of global methane and nitrogen cycles, but also provided new technology options for removal of nitrate from nitrate-contaminated water. Previous studies have demonstrated DAMO organisms could remove nitrate and nitrite from wastewater under strictly anaerobically conditions. In the study, we investigate the feasibility of nitrate removal from groundwater, which contains dissolved oxygen in addition to nitrate. A membrane biofilm reactor (MBfR), inoculated with DAMO co-culture, was capable of treating synthetic groundwater containing highly contaminated nitrate (50 mg N/L) and oxygen (7-9 mg O
Anaerobic oxidation of propane coupled to nitrate reduction by a lineage within the class Symbiobacteriia
Publisher: Springer Science and Business Media LLC
Date: 17-10-2022
DOI: 10.1038/S41467-022-33872-Y
Abstract: Anaerobic microorganisms are thought to play a critical role in regulating the flux of short-chain gaseous alkanes (SCGAs including ethane, propane and butane) from terrestrial and aquatic ecosystems to the atmosphere. Sulfate has been confirmed to act as electron acceptor supporting microbial anaerobic oxidation of SCGAs, yet several other energetically more favourable acceptors co-exist with these gases in anaerobic environments. Here, we show that a bioreactor seeded with biomass from a wastewater treatment facility can perform anaerobic propane oxidation coupled to nitrate reduction to dinitrogen gas and ammonium. The bioreactor was operated for more than 1000 days, and we used 13 C- and 15 N-labelling experiments, metagenomic, metatranscriptomic, metaproteomic and metabolite analyses to characterize the microbial community and the metabolic processes. The data collectively suggest that a species representing a novel order within the bacterial class Symbiobacteriia is responsible for the observed nitrate-dependent propane oxidation. The closed genome of this organism, which we designate as ‘ Candidatus Alkanivorans nitratireducens’, encodes pathways for oxidation of propane to CO 2 via fumarate addition, and for nitrate reduction, with all the key genes expressed during nitrate-dependent propane oxidation. Our results suggest that nitrate is a relevant electron sink for SCGA oxidation in anaerobic environments, constituting a new microbially-mediated link between the carbon and nitrogen cycles.
Elucidating functional microorganisms and metabolic mechanisms in a novel engineered ecosystem integrating C, N, P and S biotransformation by metagenomics
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.WATRES.2018.10.061
Abstract: Denitrifying sulfur conversion-associated enhanced biological phosphorous removal (DS-EBPR) system is not only a novel wastewater treatment process, but also an ideal model for microbial ecology in a community context. However, it exists the knowledge gap on the roles and interactions of functional microorganisms in the DS-EBPR system for carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) bioconversions. We use genome-resolved metagenomics to build up an ecological model of microbial communities in a lab-scale DS-EBPR system with stable operation for more than 400 days. Our results yield 11 near-complete draft genomes that represent a substantial portion of the microbial community (39.4%). Sulfate-reducing bacteria (SRB) and sulfide-oxidizing bacteria (SOB) promote complex metabolic processes and interactions for C, N, P and S conversions. Bins 1-4 and 10 are considered as new potential polyphosphate-accumulating organisms (PAOs), in which Bins 1-4 can be considered as S-related PAOs (S-PAOs) with no previously cultivated or reported members. Our findings give an insight into a new ecological system with C, N, P and S simultaneous bioconversions and improve the understanding of interactions among SRB, SOB, denitrifiers and PAOs within a community context.
Metallic nanoparticles and ions accelerate the uptake of extracellular antibiotic resistance genes through transformation
Publisher: Research Square Platform LLC
Date: 09-01-2020
Abstract: Background: Antibiotic resistance genes (ARGs), heavy metal ions and nanoparticles (NPs) are emerging and ubiquitous contaminants in the environment. However, little is known about whether heavy metal-based NPs or ions could facilitate the dissemination of ARGs through natural transformation. This study evaluated the contributions of heavy metal-based NPs (Ag NPs, CuO NPs and ZnO NPs) and their ion forms (Ag + , Cu 2+ and Zn 2+ ) to the transformation of extracellular ARGs in Acinetobacter baylyi ADP1. Results: We found that these commonly-used NPs and ions from environmentally relevant concentrations can significantly promote the natural transformation frequency of ARGs by a factor of 11.0-folds, which is comparable to the effects of antibiotics. The enhanced transformation by Ag NPs, CuO NPs, Ag + and Cu 2+ was primarily associated with reactive oxygen species (ROS) over-production and cell membrane damage, which was also evident from up-regulations of both transcription and translation of ROS and outer membrane-related genes. Additionally, transmission electron microscope imaging revealed the roughened cell membrane after Ag NPs, CuO NPs, Ag + and Cu 2+ exposure. ZnO NPs and Zn 2+ might increase the natural transformation rate by stimulating the stress response and ATP synthesis. All tested NPs and ions resulted in up-regulating the competence and SOS response-associated genes. Conclusions: Our results demonstrate that Ag, CuO and ZnO-based NPs/ions from environmental concentrations could promote the natural transformation of plasmid-encoded ARGs into naturally competent A. baylyi . Our findings provide insights into the contributions of heavy metals and NPs to the spread of antibiotic resistance.
Prediction of Filamentous Sludge Bulking using a State-based Gaussian Processes Regression Model
Publisher: Springer Science and Business Media LLC
Date: 08-08-2016
DOI: 10.1038/SREP31303
Abstract: Activated sludge process has been widely adopted to remove pollutants in wastewater treatment plants (WWTPs). However, stable operation of activated sludge process is often compromised by the occurrence of filamentous bulking. The aim of this study is to build a proper model for timely diagnosis and prediction of filamentous sludge bulking in an activated sludge process. This study developed a state-based Gaussian Process Regression (GPR) model to monitor the filamentous sludge bulking related parameter, sludge volume index (SVI), in such a way that the evolution of SVI can be predicted over multi-step ahead. This methodology was validated with SVI data collected from one full-scale WWTP. Online diagnosis and prediction of filamentous bulking sludge with real-time SVI prediction was tested through a simulation study. The results showed that the proposed methodology was capable of predicting future SVIs with good accuracy, thus providing sufficient time for predicting and controlling filamentous sludge bulking.
Achieving complete nitrogen removal by coupling nitritation-anammox and methane-dependent denitrification: A model-based study
Publisher: Wiley
Date: 20-11-2016
DOI: 10.1002/BIT.25866
Abstract: The discovery of denitrifying anaerobic methane oxidation (DAMO) processes enables the complete nitrogen removal from wastewater by utilizing the methane produced on site from anaerobic digesters. This model-based study investigated the mechanisms and operational window for efficient nitrogen removal by coupling nitritation-anaerobic ammonium oxidation (Anammox) and methane-dependent denitrification in membrane biofilm reactors (MBfRs). A mathematical model was applied to describe the microbial interactions among Anammox bacteria, DAMO archaea, and DAMO bacteria. The model sufficiently described the batch experimental data from an MBfR containing an Anammox-DAMO biofilm with different feeding nitrogen compositions, which confirmed the validity of the model. The effects of process parameters on the system performance and microbial community structure could therefore be reliably evaluated. The impacts of nitritation produced NO2(-)/NH4(+) ratio, methane supply, biofilm thickness and total nitrogen (TN) surface loading were comprehensively investigated with the model. Results showed that the optimum NO2(-)/NH4(+) ratio produced from nitritation for the Anammox-DAMO biofilm system was around 1.0 in order to achieve the maximum TN removal (over 99.0%), independent on TN surface loading. The corresponding optimal methane supply increased while the associated methane utilization efficiency decreased with the increase of TN surface loading. The cooperation between DAMO organisms and Anammox bacteria played the key role in the TN removal. Based on these results, the proof-of-concept feasibility of a single-stage MBfR coupling nitritation-Anammox-DAMO for complete nitrogen removal was also tested through integrating the model with ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) processes whilst controlling the dissolved oxygen (DO) concentration in the simulated system. The maximum TN removal was found to be achieved at the bulk DO concentration of around 0.17 g m(-3) under the simulation conditions, with the AOB, Anammox bacteria and DAMO organisms coexisting in the biofilm.
High-level nitrogen removal by simultaneous partial nitritation, anammox and nitrite/nitrate-dependent anaerobic methane oxidation
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.WATRES.2019.115057
Abstract: While the anaerobic ammonium oxidation (anammox) process has been applied for nitrogen removal from high-strength wastewater, nitrate accumulation in effluent still represents a major concern. Here, a novel process, named the one-stage PNAM, that integrates the Partial Nitritation (PN), Anammox and Methane-dependent nitrite/nitrate reduction reactions in a single membrane biofilm reactor (MBfR) is developed. With feeding of 1030 mg NH4+-N/L at a hydraulic retention time of 16 h, the proposed one-stage PNAM process achieved an average total nitrogen removal efficiency of 98% and a nitrogen removal rate of 1.5 kg N/m3/d (1.4-1.8 g N/m2/d) by using methane as the sole carbon-based electron donor. The N2O emission was determined to be 0.34% ± 0.01%. Microbial community characterization revealed that ammonia-oxidizing bacteria (AOB), anammox bacteria, nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) bacteria and archaea co-developed in the biofilm. Batch tests showed that AOB, anammox bacteria and n-DAMO microorganisms were indeed jointly responsible for the nitrogen removal. This one-stage PNAM process can potentially be applied to treating high-strength wastewater, such as anaerobic sludge digestion liquor or landfill leachate.
Modeling of the interaction among aerobic ammonium-oxidizing archaea/bacteria and anaerobic ammonium-oxidizing bacteria
Publisher: Elsevier BV
Date: 08-2016
Metatranscriptomic analysis of adaptive response of anammox bacteria Candidatus ‘Kuenenia stuttgartiensis’ to Zn(II) exposure
Publisher: Elsevier BV
Date: 05-2020
DOI: 10.1016/J.CHEMOSPHERE.2019.125682
Abstract: Zn(II) is frequently detected in biological nitrogen removal systems treating high-strength wastewater (e.g., landfill leachate), yet the cellular defense strategies of anammox bacteria against Zn(II) cytotoxicity is largely unknown. To uncover survival mechanisms under Zn(II) stress, responses of enriched anammox bacteria Candidatus 'Kuenenia stuttgartiensis' under exposure of various levels of Zn (II) were investigated through metatranscriptomic sequencing. Although increasing Zn(II) levels (50, 100 and 150 mg/L) resulted in decreasing anammox activities (86.1 ± 0.8%, 66.1 ± 1.4% and 43.9 ± 1.5% of the control, respectively), the viable cells in anammox sludge remained stable. Candidatus 'K. stuttgartiensis' possesses a complex network of regulatory systems to confer cells with the ability against Zn(II) toxicity, including functions related to substrate degradation, Zn(II) efflux, chelation, DNA repair, protein degradation, protein synthesis and signal transduction processes. Particularly, in order to maintain Zn(II) homeostasis, Candidatus 'K. stuttgartiensis' upregulated genes encoding RND efflux family (czcA, czcB, czcC, kustd1923 and kuste2279) for exporting Zn(II) actively. These heavy metal exporting genes could act as "sentinel genes" to detect the initial stage of Zn(II) inhibition on anammox bacteria, which might be beneficial to develop a diagnostic approach to predict the risk of operational failure when Zn(II) shock occurs.
Efficient and integrated start-up strategy for partial nitrification to nitrite treating low C/N domestic wastewater
Publisher: IWA Publishing
Date: 12-2009
DOI: 10.2166/WST.2009.619
Abstract: Nitrogen removal via the nitrite pathway has the potential of reducing the requirements for aeration consumption and carbon source. However, the development of an efficient and quick start-up strategy for partial nitrification to nitrite has proven difficult in the treatment of low strength wastewater. In this study, the feasibility of partial nitrification achieved by using real-time aeration duration control was not only demonstrated from the kinetic mechanism, but also was validated in three sequencing batch reactors (SBRs) fed with low C/N domestic wastewater. Nitrite accumulation could be achieved when aeration was terminated as soon as an inflexion pH point was reached (the dpH/dt became from negative to positive). The reduction or limitation of the NOB growth could be achieved through aeration duration control, due to leaving no extra time for NOB to convert the accumulated nitrite. The experimental operation results also showed that partial nitrification with nitrite accumulation ratios of over 80% was achieved successfully in these three reactors with process control. Fluorescence in situ hybridization (FISH) analysis indicated the reduction of NOB was achieved and AOB became the dominant nitrifying bacteria. Moreover, an integrated start-up strategy based on aeration duration control was proposed to quickly achieve partial nitrification to nitrite.
Optical sorting and cultivation of denitrifying anaerobic methane oxidation archaea
Publisher: The Optical Society
Date: 18-01-2017
DOI: 10.1364/BOE.8.000934
Hydrogen-driven microbial biogas upgrading: Advances, challenges and solutions
Publisher: Elsevier BV
Date: 06-2021
Modeling of nitrous oxide production by autotrophic ammonia-oxidizing bacteria with multiple production pathways
Publisher: American Chemical Society (ACS)
Date: 11-03-2014
DOI: 10.1021/ES405592H
Abstract: Autotrophic ammonia oxidizing bacteria (AOB) have been recognized as a major contributor to N2O production in wastewater treatment systems. However, so far N2O models have been proposed based on a single N2O production pathway by AOB, and there is still a lack of effective approach for the integration of these models. In this work, an integrated mathematical model that considers multiple production pathways is developed to describe N2O production by AOB. The pathways considered include the nitrifier denitrification pathway (N2O as the final product of AOB denitrification with NO2(-) as the terminal electron acceptor) and the hydroxylamine (NH2OH) pathway (N2O as a byproduct of incomplete oxidation of NH2OH to NO2(-)). In this model, the oxidation and reduction processes are modeled separately, with intracellular electron carriers introduced to link the two types of processes. The model is calibrated and validated using experimental data obtained with two independent nitrifying cultures. The model satisfactorily describes the N2O data from both systems. The model also predicts shifts of the dominating pathway at various dissolved oxygen (DO) and nitrite levels, consistent with previous hypotheses. This unified model is expected to enhance our ability to predict N2O production by AOB in wastewater treatment systems under varying operational conditions.
Triclosan at environmentally relevant concentrations promotes horizontal transfer of multidrug resistance genes within and across bacterial genera
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.ENVINT.2018.10.040
Abstract: Antibiotic resistance poses an increasing threat to public health. Horizontal gene transfer (HGT) promoted by antibiotics is recognized as a significant pathway to disseminate antibiotic resistance genes (ARGs). However, it is unclear whether non-antibiotic, anti-microbial (NAAM) chemicals can directly promote HGT of ARGs in the environment. We aimed to investigate whether triclosan (TCS), a widely-used NAAM chemical in personal care products, is able to stimulate the conjugative transfer of antibiotic multi-resistance genes carried by plasmid within and across bacterial genera. We established two model mating systems, to investigate intra-genera transfer and inter-genera transfer. Escherichia coli K-12 LE392 carrying IncP-α plasmid RP4 was used as the donor, and E. coli K-12 MG1655 or Pseudomonas putida KT2440 were the intra- and inter-genera recipients, respectively. The mechanisms of the HGT promoted by TCS were unveiled by detecting oxidative stress and cell membrane permeability, in combination with Nanopore sequencing, genome-wide RNA sequencing and proteomic analyses. Exposure of the bacteria to environmentally relevant concentrations of TCS (from 0.02 μg/L to 20 μg/L) significantly stimulated the conjugative transfer of plasmid-encoded multi-resistance genes within and across genera. The TCS exposure promoted ROS generation and damaged bacterial membrane, and caused increased expression of the SOS response regulatory genes umuC, dinB and dinD in the donor. In addition, higher expression levels of ATP synthesis encoding genes in E. coli and P. putida were found with increased TCS dosage. TCS could enhance the conjugative ARGs transfer between bacteria by triggering ROS overproduction at environmentally relevant concentrations. These findings improve our awareness of the hidden risks of NAAM chemicals on the spread of antibiotic resistance.
New insights of the bacterial response to exposure of differently sized silver nanomaterials
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.WATRES.2019.115205
Abstract: The release of silver nanomaterials (AgNMs) from extensive use poses potential risks to human health and ecological environments. Although previous studies have reported the negative effects of AgNMs on various microorganisms, little is known about the response of bacteria under the exposure of AgNMs at the cellular level. Here, we report the multiple responses of Pseudomonas aeruginosa PAO1 (PAO1) under the exposure of two types of AgNMs, including spherical silver nanoparticles (AgNPs) and fibrous silver nanorods (AgNRs), by physiological experiments, microscopy, synchrotron-based X-ray Absorption Spectroscopy (XAS), flow cytometry and genome-wide RNA sequencing. Our results demonstrated that the exposure to both types of AgNMs could inhibit the growth of PAO1, accompanied by the overproduction of oxidative stress and inducing cell membrane damage. Transmission electron microscopy revealed the roughened cell membrane under both AgNMs treatment. In addition, both AgNMs repressed the expression of quorum sensing and metal efflux-related genes in PAO1, but stimulated denitrification, glycerol and amino acid metabolisms, SOS response and pyocin overproduction of PAO1. Compared to AgNRs, AgNPs exposure showed a much lower threshold concentration to trigger the inhibitory effect and induced greater transcriptional responses of PAO1. This study suggested that AgNMs could cause multiple effects on the proliferation, metabolism, virulence and pathogenesis of PAO1, which might further affect the corresponding environmental microbial communities. Overall, our findings offer insights into the interactions between AgNMs and bacteria at the molecular level.
Determining the Contribution of Micro/Nanoplastics to Antimicrobial Resistance: Challenges and Perspectives
Publisher: American Chemical Society (ACS)
Date: 14-08-2023
Biogas-driven complete nitrogen removal from wastewater generated in side-stream partial nitritation
Publisher: Elsevier BV
Date: 11-2020
Correction: Non-antibiotic pharmaceuticals enhance the transmission of exogenous antibiotic resistance genes through bacterial transformation (The ISME Journal, (2020), 14, 8, (2179-2196), 10.1038/s41396-020-0679-2)
Publisher: Springer Science and Business Media LLC
Date: 02-08-2022
Plasmids Can Shift Bacterial Morphological Response against Antibiotic Stress
Publisher: Wiley
Date: 24-11-2022
Abstract: Bacterial cell filamentation is a morphological change wherein cell ision is blocked, which can improve bacterial survival under unfavorable conditions (e.g., antibiotic stress that causes DNA damage). As an extrachromosomal DNA molecule, plasmids can confer additionally advantageous traits including antibiotic resistance on the host. However, little is known about whether plasmids could shift bacterial morphological responses to antibiotic stress. Here, it is reported that plasmid‐free cells, rather than plasmid‐bearing cells, exhibit filamentation and asymmetrical cell ision under exposure to sub‐inhibitory concentrations of antibiotics (ciprofloxacin and cephalexin). The underlying mechanism is revealed by investigating DNA damage, cell ision inhibitor sulA , the SOS response, toxin‐antitoxin module ( parDE ) located on plasmids, and efflux pumps. Significantly higher expression of sulA is observed in plasmid‐free cells, compared to plasmid‐bearing cells. Plasmid carriage enables the hosts to suffer less DNA damage, exhibit stronger efflux pump activities, and thus have a higher antibiotic tolerance. These benefits are attributed to the parDE module that mediates stress responses from plasmid‐bearing cells and mainly contributes to cell morphological changes. Collectively, the findings demonstrate that plasmids can confer additional innate defenses on the host to antibiotics, thus advancing the understanding of how plasmids affect bacterial evolution in hostile environments.
Triclosan Promotes Conjugative Transfer of Antibiotic Resistance Genes to Opportunistic Pathogens in Environmental Microbiome
Publisher: American Chemical Society (ACS)
Date: 17-10-2022
Abstract: Although triclosan, as a widely used antiseptic chemical, is known to promote the transmission of antibiotic resistance to erse hosts in pure culture, it is still unclear whether and how triclosan could affect the transmission of broad-host-range plasmids among complex microbial communities. Here, bacterial culturing, fluorescence-based cell sorting, and high-throughput 16S rRNA gene licon sequencing were combined to investigate contributions of triclosan on the transfer rate and range of an IncP-type plasmid from a proteobacterial donor to an activated sludge microbiome. Our results demonstrate that triclosan significantly enhances the conjugative transfer of the RP4 plasmid among activated sludge communities at environmentally relevant concentrations. High-throughput 16S rRNA gene sequencing on sorted transconjugants demonstrates that triclosan not only promoted the intergenera transfer but also the intragenera transfer of the RP4 plasmid among activated sludge communities. Moreover, triclosan mediated the transfer of the RP4 plasmid to opportunistic human pathogens, for ex le,
Cometabolic biodegradation of cephalexin by enriched nitrifying sludge: Process characteristics, gene expression and product biotoxicity
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.SCITOTENV.2019.03.473
Abstract: The nitrifying systems have been reported to be able to biodegrade micropollutants, yet it is still unclear about the cometabolism of ammonia-oxidizing bacteria (AOB) towards micropollutants, in particular their enzyme and transcriptional responses under exposure of micropollutants. This study investigated cometabolic biodegradation of a selected antibiotic, cephalexin (CFX), by an enriched nitrifying culture through a series of batch experiments, together with the assessments of enzymatic activity, key gene expression, and biotoxicity of the degradation products. More than 99% CFX with an initial concentration of 50 μg/L could be removed with the presence of ammonium, while <44% of CFX removal was observed in the absence of ammonium, suggesting the cometabolic degradation of CFX by ammonia-oxidizing bacteria (AOB). After the addition of 50 μg/L CFX, the ammonia oxidizing rate (AOR) decreased from 36.6 to 11.0 mg N/(L·h·g VSS), followed by a slight recovery when CFX concentration decreased to below 8 μg/L. Ammonia monooxygenase (AMO) activity showed a similar trend with that of AOR. The quantitative reverse transcription PCR assay indicated that the expression level of amoA gene was significantly upregulated (up to 3-fold, p < 0.05) due to the addition of CFX, while decreased to the normal level once CFX was degraded, suggesting a mechanism of AOB to neutralize the toxicity of CFX by metabolizing ammonia more effectively. Meanwhile, the biotoxicity test showed the degradation products of CFX did not exhibit any antibacterial impacts in terms of cell viability, compared to the parent compounds. Our finding shed a light on AMO-mediated cometabolic biodegradation of antibiotics in nitrifying cultures.
A novel protocol for model calibration in biological wastewater treatment
Publisher: Springer Science and Business Media LLC
Date: 16-02-2015
DOI: 10.1038/SREP08493
Abstract: Activated sludge models (ASMs) have been widely used for process design, operation and optimization in wastewater treatment plants. However, it is still a challenge to achieve an efficient calibration for reliable application by using the conventional approaches. Hereby, we propose a novel calibration protocol, i.e. Numerical Optimal Approaching Procedure (NOAP), for the systematic calibration of ASMs. The NOAP consists of three key steps in an iterative scheme flow: i) global factors sensitivity analysis for factors fixing ii) pseudo-global parameter correlation analysis for non-identifiable factors detection and iii) formation of a parameter subset through an estimation by using genetic algorithm. The validity and applicability are confirmed using experimental data obtained from two independent wastewater treatment systems, including a sequencing batch reactor and a continuous stirred-tank reactor. The results indicate that the NOAP can effectively determine the optimal parameter subset and successfully perform model calibration and validation for these two different systems. The proposed NOAP is expected to use for automatic calibration of ASMs and be applied potentially to other ordinary differential equations models.
Aerobic condition enhances bacteriostatic effects of silver nanoparticles in aquatic environment: An antimicrobial study on Pseudomonas aeruginosa
Publisher: Springer Science and Business Media LLC
Date: 07-08-2017
DOI: 10.1038/S41598-017-07989-W
Abstract: The intensive applications of silver nanoparticles (AgNPs) inevitably cause continuous release of such materials into environments, as a consequence posing potential risks to microbial communities in engineered or natural ecosystems. However, the magnitude of antibacterial capacity of nanoparticles is still inconclusive, owing to influential factors such as the size of nanoparticle, microbial species, or environmental conditions. To reveal whether the presence of air would alter AgNPs ecotoxicity, Pseudomonas aeruginosa PAO1, a facultative denitrifying bacterium and an opportunity pathogen, was used to study antibacterial assays under both anaerobic and aerobic conditions. The results indicate that the respiration status of P. aeruginosa affect the ecotoxicity of AgNPs. P. aeruginosa cultured under aerobic condition were more susceptible to AgNPs than that under anaerobic condition. Aerobic condition greatly enhanced bacteriostatic effects of AgNPs but not their bactericidal effects, as the ratio of viable but nonculturable (VBNC) bacteria remained above 90% when 5 mg L −1 AgNPs applied. Our findings offer further understanding for the degree of toxicity of nanoparticles on microbial ecosystems and underscore the importance of exposure condition (e.g. oxygen) in the mode of action of AgNPs.
The presence of plasmids in bacterial hosts alters phage isolation and infectivity
Publisher: Springer Science and Business Media LLC
Date: 19-08-2022
DOI: 10.1038/S43705-022-00158-9
Abstract: Antibiotic resistance genes are often carried by plasmids, which spread intra- and inter genera bacterial populations, and also play a critical role in bacteria conferring phage resistance. However, it remains unknown about the influence of plasmids present in bacterial hosts on phage isolation and subsequent infectivity. In this study, using both Escherichia coli and Pseudomonas putida bacteria containing different plasmids, eight phages were isolated and characterized in terms of phage morphology and host range analysis, in conjunction with DNA and protein sequencing. We found that plasmids can influence both the phage isolation process and phage infectivity. In particular, the isolated phages exhibited different phage plaquing infectivity towards the same bacterial species containing different plasmids. Furthermore, the presence of plasmids was found to alter the expression of bacteria membrane protein, which correlates with bacterial cell surface receptors recognized by phages, thus affecting phage isolation and infectivity. Given the erse and ubiquitous nature of plasmids, our findings highlight the need to consider plasmids as factors that can influence both phage isolation and infectivity.
Combination process of limited filamentous bulking and nitrogen removal via nitrite for enhancing nitrogen removal and reducing aeration requirements
Publisher: Elsevier BV
Date: 03-2013
DOI: 10.1016/J.CHEMOSPHERE.2012.12.004
Abstract: Limited filamentous bulking (LFB) activated sludge process was proposed by Guo et al. (2010) to increase the removal of tiny suspended particulates in the clarifier and reduce aeration energy consumption. However, when the use of LFB process, ammonium removal efficiency would be compromised due to low dissolved oxygen (DO). In this study, the combination process of nitrogen removal via nitrite and LFB was achieved to enhance nitrogen removal and reduce aeration energy consumption by controlling low DO levels (0.5-1.0 mg L(-1)) in a lab-scale anoxic-oxic reactor (V=66 L) treating real domestic wastewater at room temperature. Above 85% of nitrite accumulation ratio was steadily maintained during continuous operation period. The combined process improved the total nitrogen (TN) removal by about 20% in comparison to the traditional process via the nitrate pathway, and also reduced the specific aeration energy consumption by 35%. COD, ammonium and TN removal efficiencies were up to 86%, 94% and 75%, respectively. The process proved effective in achieving a steady LFB state, whereby sludge volume index between 150 and 250 mL g(-1) was sustained for long-term operation. The microbial community structure was analyzed by fluorescence in situ hybridization, which indicated ammonia-oxidizing bacteria out-competed nitrite-oxidizing bacteria. Moreover, the filaments Type 0041 and Microthrix parvicella proliferated with limited abundance. The results indicated the combination process of LFB and nitrogen removal via nitrite under low DO was a feasible solution for saving energy and enhancing nitrogen removal when treating domestic wastewater.
Amphiphilic Perfluoropolyether Copolymers for the Effective Removal of Polyfluoroalkyl Substances from Aqueous Environments
Publisher: American Chemical Society (ACS)
Date: 16-03-2021
Light Irradiation Enables Rapid Start-Up of Nitritation through Suppressing nxrB Gene Expression and Stimulating Ammonia-Oxidizing Bacteria
Publisher: American Chemical Society (ACS)
Date: 16-09-2021
Making good use of methane to remove oxidized contaminants from wastewater
Publisher: Elsevier BV
Date: 06-2021
An evolved native microalgal consortium-snow system for the bioremediation of biogas and centrate wastewater: Start-up, optimization and stabilization
Publisher: Elsevier BV
Date: 05-2021
Reactive nitrogen species from free nitrous acid (FNA) cause cell lysis
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.WATRES.2022.118401
Abstract: Free nitrous acid (FNA, i.e. HNO
Short- and long-term effects of temperature on partial nitrification in a sequencing batch reactor treating domestic wastewater
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.JHAZMAT.2010.03.027
Abstract: Partial nitrification to nitrite has been frequently obtained at high temperatures, but has proved difficult to achieve at low temperatures when treating low strength domestic wastewater. In this study, the long-term effects of temperature on partial nitrification were investigated by operating a sequencing bath reactor with the use of aeration duration control. The specific ammonia oxidation rate decreased by 1.5 times with the temperature decreasing from 25 to 15 degrees C. However, low temperature did not deteriorate the stable partial nitrification performance. Nitrite accumulation ratio was always above 90%, even slightly higher (above 95%) at low temperatures. The nitrifying sludge accumulated with ammonia-oxidizing bacteria (AOB), but washout of nitrite-oxidizing bacteria (NOB) was used to determine the short-term effects of temperature on ammonia oxidation process. The ammonia oxidation rate depended more sensitively on lower temperatures correspondingly the temperature coefficient theta was 1.172 from 5 to 20 degrees C, while theta was 1.062 from 20 to 35 degrees C. Moreover, the larger activation energy (111.5 kJ mol(-1)) was found at lower temperatures of 5-20 degrees C, whereas the smaller value (42.0 kJ mol(-1)) was observed at higher temperatures of 20-35 degrees C. These findings might be contributed to extend the applicability of the partial nitrification process in wastewater treatment plants operated under cold weather conditions. It is suggested that the selective enrichment of AOB as well as the washout of NOB be obtained by process control before making the biomass slowly adapt to low temperatures for achieving partial nitrification to nitrite at low temperatures.
Long-term effect of dissolved oxygen on partial nitrification performance and microbial community structure
Publisher: Elsevier BV
Date: 06-2009
DOI: 10.1016/J.BIORTECH.2008.12.036
Abstract: In this study, the performance of partial nitrification via nitrite and microbial community structure were investigated and compared in two sequencing batch reactors (SBR) with different dissolved oxygen (DO) levels. Both reactors achieved stable partial nitrification with nitrite accumulation ratio of above 95% by using real-time aeration duration control. Compared with high DO (above 3 mg/l on average) SBR, simultaneous nitrification and denitrification (SND) via nitrite was carried out in low DO (0.4-0.8 mg/l) SBR. The average efficiencies of SND in high DO and low DO reactor were 7.7% and 44.9%, and the specific SND rates were 0.20 and 0.83 mg N/(mg MLSS h), respectively. Low DO did not produce sludge with poorer settling properties but attained lower turbidities of the effluent than high DO. Fluorescence in situ hybridization (FISH) analysis in both the reactors showed that ammonia-oxidizing bacteria (AOB) were the dominant nitrifying bacteria and nitrite-oxidizing bacteria (NOB) did not be recovered in spite of exposing nitrifying sludge to high DO. The morphology of the sludge from both two reactors according to scanning electron microscope indicated that small rod-shaped and spherical clusters were dominant, although filamentous bacteria and few long rod-shaped coexisted in the low DO reactor. By selecting properly DO level and adopting process control method is not only of benefit to the achievement of novel biological nitrogen removal technology, but also favorable to sludge population optimization.
A methanotrophic archaeon couples anaerobic oxidation of methane to Fe(III) reduction
Publisher: Springer Science and Business Media LLC
Date: 16-04-2018
Dissolved organic matter in biologically treated sewage effluent (BTSE): Characteristics and comparison
Publisher: Elsevier BV
Date: 09-2011
Roles of Oxygen in Methane-dependent Selenate Reduction in a Membrane Biofilm Reactor: Stimulation or Suppression
Publisher: Elsevier BV
Date: 06-2021
Microbial nitrate reduction in propane- or butane-based membrane biofilm reactors under oxygen-limiting conditions
Publisher: Elsevier BV
Date: 05-2023
Comparison of short-term dosing ferrous ion and nanoscale zero-valent iron for rapid recovery of anammox activity from dissolved oxygen inhibition
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.WATRES.2019.01.029
Abstract: As obligate anaerobes, anammox bacteria are sensitive to oxygen, which might hinder the maximization of anammox activity. However, there are very few effective strategies to rapidly recover anammox activity after its deterioration under exposure of oxygen. In this study, the activity recovery of anammox bacteria encountering dissolved oxygen (DO) exposure (0.2 and 2.0 mg L
Simultaneous Removal of Dissolved Methane and Nitrogen from Synthetic Mainstream Anaerobic Effluent
Publisher: American Chemical Society (ACS)
Date: 20-05-2020
Metagenomic analysis of anammox communities in three different microbial aggregates
Publisher: Wiley
Date: 18-01-2016
Abstract: There is great potential to understand the functional ersity of microorganisms that are involved in waste water treatment through metagenomic analyses. This study presents the first metagenomic comparison of taxonomic and functional profiles of the microbial communities occurring in different aggregates from anaerobic ammonium-oxidizing (anammox) bioreactors. The anammox bacterial communities in both biofilm and granule sludge s les showed relatively high abundance and ersity compared with floccular sludge. Four of the five known genera of anammox bacteria were detected in the three cultures except Candidatus Jettenia, which was absent in the granules. Candidatus Kuenenia comprised the major population of anammox bacteria in these three sludges, independent of their growth morphologies. The genome assembled for the Candidatus Kuenenia in the granule was very similar to the published reference genome of Candidatus K. stuttgartiensis. Genes involved in the metabolism of the anammox process were highly detected in the biofilm and granule sludges. In particular, the abundance of hydrazine synthase gene (hzs) in the biofilm was around 486 times more pronounced than that in the granules. The knowledge gained in this study highlights an important role of sludge aggregate in affecting community structure and metabolic potential of anammox systems.
Microbial Selenate Reduction Driven by a Denitrifying Anaerobic Methane Oxidation Biofilm
Publisher: American Chemical Society (ACS)
Date: 13-03-2018
Abstract: Anaerobic oxidation of methane (AOM) plays a crucial role in controlling the flux of methane from anoxic environments. Sulfate-, nitrite-, nitrate-, and iron-dependent methane oxidation processes have been considered to be responsible for the AOM activities in anoxic niches. We report that nitrate-reducing AOM microorganisms, enriched in a membrane biofilm bioreactor, are able to couple selenate reduction to AOM. According to ion chromatography, X-ray photoelectron spectroscopy, and long-term bioreactor performance, we reveal that soluble selenate was reduced to nanoparticle elemental selenium. High-throughput 16S rRNA gene sequencing indicates that Candidatus Methanoperedens and Candidatus Methylomirabilis remained the only known methane-oxidizing microorganisms after nitrate was switched to selenate, suggesting that these organisms could couple anaerobic methane oxidation to selenate reduction. Our findings suggest a possible link between the biogeochemical selenium and methane cycles.
Structural changes in model compounds of sludge extracellular polymeric substances caused by exposure to free nitrous acid
Publisher: Elsevier BV
Date: 2021
Acetate Production from Anaerobic Oxidation of Methane via Intracellular Storage Compounds
Publisher: American Chemical Society (ACS)
Date: 04-06-2019
Abstract: There is great interest in microbial conversion of methane, an abundant resource, into valuable liquid chemicals. While aerobic bioconversion of methane to liquid chemicals has been reported, studies of anaerobic methane bioconversion to liquid chemicals are rare. Here we show that a microbial culture dominated by Candidatus 'Methanoperedens nitroreducens', an anaerobic methanotrophic archaeon, anaerobically oxidizes methane to produce acetate, indirectly via reaction intermediate(s), when nitrate or nitrite is supplied as an electron acceptor under a rate-limiting condition. Isotopic labeling tests showed that acetate was produced from certain intracellular storage compounds that originated from methane. Fluorescence in situ hybridization and Nile red staining demonstrated that polyhydroxyalkanoate in M. nitroreducens was likely one of the intracellular storage compounds for acetate production, along with glycogen. Acetate is a common substrate for the production of more valuable chemicals. The microbial conversion discovered in this study potentially enables a new approach to the use of methane as a feedstock for the chemical market.
Determining Multiple Responses of Pseudomonas aeruginosa PAO1 to an Antimicrobial Agent, Free Nitrous Acid
Publisher: American Chemical Society (ACS)
Date: 04-05-2016
Abstract: Free nitrous acid (FNA) has recently been demonstrated as an antimicrobial agent on a range of micro-organisms, especially in wastewater-treatment systems. However, the antimicrobial mechanism of FNA is largely unknown. Here, we report that the antimicrobial effects of FNA are multitargeted. The response of a model denitrifier, Pseudomnas aeruginosa PAO1 (PAO1), common in wastewater treatment, was investigated in the absence and presence of inhibitory level of FNA (0.1 mg N/L) under anaerobic denitrifying conditions. This was achieved through coupling gene expression analysis, by RNA sequencing, and with a suite of physiological analyses. Various transcripts exhibited significant changes in abundance in the presence of FNA. Respiration was likely inhibited because denitrification activity was severely depleted, and decreased transcript levels of most denitrification genes occurred. As a consequence, the tricarboxylic acid (TCA) cycle was inhibited due to the lowered cellular redox state in the FNA-exposed cultures. Meanwhile, during FNA exposure, PAO1 rerouted its carbon metabolic pathway from the TCA cycle to pyruvate fermentation with acetate as the end product as a possible survival mechanism. Additionally, protein synthesis was significantly decreased, and ribosome preservation was evident. These findings improve our understanding of PAO1 in response to FNA and contribute toward the potential application for use of FNA as an antimicrobial agent.
Vertical up-flow constructed wetlands exhibited efficient antibiotic removal but induced antibiotic resistance genes in effluent
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.CHEMOSPHERE.2018.04.006
Abstract: The intensive use of antibiotics results in their continuous release into the environment and the subsequent widespread dissemination of antibiotic resistance genes (ARGs), thus posing potential risks for public health. Although vertical up-flow constructed wetlands (VUF-CWs) have been widely used to treat wastewater in remote or rural regions, few studies have assessed the potential risks of ARG dissemination when VUF-CWs are applied to treat wastewaters containing antibiotics. In this study, the removal performance of two typical antibiotics (sulfamethoxazole (SMX) and tetracycline (TC)) and the fate of ARGs were evaluated in three lab-scale VUF-CWs. The results indicated that high removal efficiencies (>98%) could be achieved for both SMX and TC. However, the exposure of antibiotics resulted in harboring abundant ARGs (mainly sul- and tet-related genes), even with increasing abundances with operation time. The abundances of ARGs had a positive correlation with the accumulation of SMX and TC in different layers of VUF-CWs, where the tet and sul genes have the highest abundance in the bottom layer due to the highest antibiotic exposure concentration. Positive correlations were observed between the abundance of tet gene and antibiotic concentration in effluent. Although the effluent had lower abundances of the ARGs than that in the wetland media, the occurrence of ARGs in effluent might still pose risk for public health. Further studies are required to explore effective control strategies to eliminate ARGs from VUF-CWs.
Simultaneous Removal of Antibiotic Resistant Bacteria, Antibiotic Resistance Genes, and Micropollutants by FeS2@GO-Based Heterogeneous Photo-Fenton Process
Publisher: American Chemical Society (ACS)
Date: 27-06-2022
Abstract: The co-occurrence of various chemical and biological contaminants of emerging concerns has hindered the application of water recycling. This study aims to develop a heterogeneous photo-Fenton treatment by fabricating nano pyrite (FeS
Correction to: Non-antibiotic pharmaceuticals promote the transmission of multidrug resistance plasmids through intra- and intergenera conjugation (The ISME Journal, (2021), 15, 9, (2493-2508), 10.1038/s41396-021-00945-7)
Publisher: Springer Science and Business Media LLC
Date: 02-08-2022
Antiepileptic drug carbamazepine promotes horizontal transfer of plasmid-borne multi-antibiotic resistance genes within and across bacterial genera
Publisher: Springer Science and Business Media LLC
Date: 05-10-2019
Structural Changes in Cell-Wall and Cell-Membrane Organic Materials Following Exposure to Free Nitrous Acid
Publisher: American Chemical Society (ACS)
Date: 06-08-2020
Chlorine disinfection increases both intracellular and extracellular antibiotic resistance genes in a full-scale wastewater treatment plant
Publisher: Elsevier BV
Date: 06-2018
DOI: 10.1016/J.WATRES.2018.02.036
Abstract: The emergence and spread of antibiotic resistance has posed a major threat to both human health and environmental ecosystem. Although the disinfection has been proved to be efficient to control the occurrence of pathogens, little effort is dedicated to revealing potential impacts of disinfection on transmission of antibiotic resistance genes (ARGs), particularly for free-living ARGs in final disinfected effluent of urban wastewater treatment plants (UWWTP). Here, we investigated the effects of chlorine disinfection on the occurrence and concentration of both extracellular ARGs (eARGs) and intracellular ARGs (iARGs) in a full-scale UWWTP over a year. We reported that the concentrations of both eARGs and iARGs would be increased by the disinfection with chlorine dioxide (ClO
Nonnutritive sweeteners can promote the dissemination of antibiotic resistance through conjugative gene transfer
Publisher: Springer Science and Business Media LLC
Date: 15-02-2021
DOI: 10.1038/S41396-021-00909-X
Abstract: Antimicrobial resistance (AMR) poses a worldwide threat to human health and biosecurity. The spread of antibiotic resistance genes (ARGs) via conjugative plasmid transfer is a major contributor to the evolution of this resistance. Although permitted as safe food additives, compounds such as saccharine, sucralose, aspartame, and acesulfame potassium that are commonly used as nonnutritive sweeteners have recently been associated with shifts in the gut microbiota similar to those caused by antibiotics. As antibiotics can promote the spread of antibiotic resistance genes (ARGs), we hypothesize that these nonnutritive sweeteners could have a similar effect. Here, we demonstrate for the first time that saccharine, sucralose, aspartame, and acesulfame potassium could promote plasmid-mediated conjugative transfer in three established conjugation models between the same and different phylogenetic strains. The real-time dynamic conjugation process was visualized at the single-cell level. Bacteria exposed to the tested compounds exhibited increased reactive oxygen species (ROS) production, the SOS response, and gene transfer. In addition, cell membrane permeability increased in both parental bacteria under exposure to the tested compounds. The expression of genes involved in ROS detoxification, the SOS response, and cell membrane permeability was significantly upregulated under sweetener treatment. In conclusion, exposure to nonnutritive sweeteners enhances conjugation in bacteria. Our findings provide insight into AMR spread and indicate the potential risk associated with the presence of nonnutritive sweeteners.
Temperature-Tolerated Mainstream Nitrogen Removal by Anammox and Nitrite/Nitrate-Dependent Anaerobic Methane Oxidation in a Membrane Biofilm Reactor
Publisher: American Chemical Society (ACS)
Date: 08-02-2020
Suspended sludge and biofilm shaped different anammox communities in two pilot-scale one-stage anammox reactors
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.BIORTECH.2016.03.049
Abstract: The abundance and ersity of anammox bacteria was investigated in two pilot-scale integrated fixed-film activated sludge (IFAS) reactors treating high ammonium wastewater. Reactor A was inoculated with nitrifying sludge, while Reactor B was inoculated with suspended anammox sludge with the dominant anammox bacteria of Candidatus 'Kuenenia'. After 180days' operation, the predominate anammox bacteria was Candidatus 'Brocadia' (65%) in the biofilm, while Candidatus 'Kuenenia' (86%) outcompeted with other anammox bacteria in suspended sludge in Reactor A. Candidatus 'Kuenenia' were dominated in suspended sludge through the entire experiment in Reactor B. In contrast, the predominated species shifted from Candidatus 'Kuenenia' (89%) into Candidatus 'Brocadia' (66%) in the biofilm of Reactor B. This study indicated that Candidatus 'Brocadia' preferred to grow in the biofilm, while Candidatus 'Kuenenia' would dominant over other anammox bacteria in the suspended sludge. Further studies are required to identify the internal factors affecting the distribution of anammox bacteria.
Biological nitrogen removal with real-time control using step-feed SBR technology
Publisher: Elsevier BV
Date: 05-2007
Effects of feeding pattern and dissolved oxygen concentration on microbial morphology and community structure: The competition between floc-forming bacteria and filamentous bacteria
Publisher: Elsevier BV
Date: 04-2014
Physiological and transcriptomic analyses reveal CuO nanoparticle inhibition of anabolic and catabolic activities of sulfate-reducing bacterium
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.ENVINT.2019.01.058
Abstract: The widespread use of CuO nanoparticles (NPs) results in their continuous release into the environment, which could pose risks to public health and to microbial ecosystems. Following consumption, NPs will initially enter into sewer systems and interact with and potentially influence sewer microbial communities. An understanding of the response of microbes in sewers, particularly sulfate-reducing bacteria (SRB), to the CuO NPs induced stress is important as hydrogen sulfide produced by SRB can cause sewer corrosion and odour emissions. In this study, we elucidated how the anabolic and catabolic processes of a model SRB, Desulfovibrio vulgaris Hidenborough (D. vulgaris), respond to CuO NPs. Physiological analyses indicated that the exposure of the culture to CuO NPs at elevated concentrations (>50 mg/L) inhibited both its anabolic and catabolic activities, as revealed by lowered cell proliferation and sulfate reduction rate. The antibacterial effects of CuO NPs were mainly attributed to the overproduction of reactive oxygen species. Transcriptomic analysis indicated that genes encoding for flagellar assembly and some genes involved in electron transfer and respiration were down-regulated, while genes for the ferric uptake regulator (Fur) were up-regulated. Moreover, the CuO NPs exposure significantly up-regulated genes involved in protein synthesis and ATP synthesis. These results suggest that CuO NPs inhibited energy conversion, cell mobility, and iron starvation to D. vulgaris. Meanwhile, D. vulgaris attempted to respond to the stress of CuO NPs by increasing protein and ATP synthesis. These findings offer new insights into the bacterial-nanoparticles interaction at the transcriptional level, and advance our understanding of impacts of CuO NPs on SRB in the environment.
Advanced nitrogen removal by pulsed sequencing batch reactors (SBR) with real-time control
Publisher: Springer Science and Business Media LLC
Date: 10-2007
Enhanced nutrient removal in a modified step feed process treating municipal wastewater with different inflow distribution ratios and nutrient ratios
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.BIORTECH.2010.06.151
Abstract: A pilot-scale modified step feed process was proposed to enhance organics and nutrient (N and P) removal performance from municipal wastewater. It combined University of Cape Town (UCT) and step feed process. Effects of inflow distribution ratios and nutrients ratios were investigated. The highest removal efficiencies of 89% for chemical oxygen demanding (COD), 88% for total nitrogen (TN) and 93% for phosphorus were obtained, respectively, at the inflow distribution ratio of 40:30:30%. The phosphorus removal exhibited an upward trend with the increasing of influent COD/P and TN/P, and the nitrogen removal had a positive correlation with influent COD/TN. In addition, aerobic simultaneous nitrification and denitrification and anoxic denitrifying phosphorus uptake made a distinct contribution to enhance nutrient removal. The proposed system was demonstrated to be an attractive enhanced biological nutrient removal process for wastewater treatment plants due to relatively high nutrient removal, robust sludge settleability and energy savings.
Modeling of simultaneous anaerobic methane and ammonium oxidation in a membrane biofilm reactor
Publisher: American Chemical Society (ACS)
Date: 31-07-2014
DOI: 10.1021/ES502608S
Abstract: Nitrogen removal by using the synergy of denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox) microorganisms in a membrane biofilm reactor (MBfR) has previously been demonstrated experimentally. In this work, a mathematical model is developed to describe the simultaneous anaerobic methane and ammonium oxidation by DAMO and Anammox microorganisms in an MBfR for the first time. In this model, DAMO archaea convert nitrate, both externally fed and/or produced by Anammox, to nitrite, with methane as the electron donor. Anammox and DAMO bacteria jointly remove the nitrite fed roduced, with ammonium and methane as the electron donor, respectively. The model is successfully calibrated and validated using the long-term (over 400 days) dynamic experimental data from the MBfR, as well as two independent batch tests at different operational stages of the MBfR. The model satisfactorily describes the methane oxidation and nitrogen conversion data from the system. Modeling results show the concentration gradients of methane and nitrogen would cause stratification of the biofilm, where Anammox bacteria mainly grow in the biofilm layer close to the bulk liquid and DAMO organisms attach close to the membrane surface. The low surface methane loadings result in a low fraction of DAMO microorganisms, but the high surface methane loadings would lead to overgrowth of DAMO bacteria, which would compete with Anammox for nitrite and decrease the fraction of Anammox bacteria. The results suggest an optimal methane supply under the given condition should be applied not only to benefit the nitrogen removal but also to avoid potential methane emissions.
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