Identification of antibiotic resistant bacteria community and a GeoChip based study of resistome in urban watersheds

Unexpected enrichment of antibiotic resistance genes and organic remediation genes in high-altitude lakes at Eastern Tibetan Plateau

Elevation has a strong effect on aquatic microbiome. However, we know little about the effects of elevation on functional genes, especially antibiotic resistance genes (ARGs) and organic remediation genes (ORGs) in freshwater ecosystems. In this study, we analyzed five classes of functional genes including ARGs, metal resistance genes (MRGs), ORGs, bacteriophages, and virulence genes between two high-altitude lakes (HALs) and two low-altitude lakes (LALs) in Mountain Siguniang at Eastern Tibetan Plateau by means of GeoChip 5.0. No differences (Student's t-test, p > 0.05) of gene richness including ARGs, MRGs, ORGs, bacteriophages, and virulence genes in HALs and LALs were found. The abundance of most ARGs and ORGs was higher in HALs than in LALs. For MRGs, the abundance of macro metal resistance genes of potassium, calcium, and aluminum was higher in HALs than in LALs (Student's t-test, p < 0.05; all Cohen's d > 0.8). The abundance of some heavy metal resistance genes of lead and mercury was lower in HALs than in LALs (Student's t-test, p < 0.05; all Cohen's d < -0.8). The composition of these functional genes in HALs differed significantly from in LALs. The functional gene network in HALs was also more complex than that in LALs. We speculate that enrichment of ARGs and ORGs in HALs is related to different microbial communities, exogenous ARGs, and enriched persistent organic pollutants through long-range atmospheric transport driven by the Indian monsoon. This study highlights the unexpected enrichment of ARGs, MRGs, and ORGs in remote lakes at high elevations.

Antibiotic resistant bacteria: A bibliometric review of literature

Antibiotic-resistant bacteria (ARB) are a serious threat to the health of people and the ecological environment. With this problem becoming more and more serious, more countries made research on the ARB, and the research number has been sharply increased particularly over the past decade. Therefore, it is quite necessary to globally retrace relevant researches on the ARB published from 2010 to 2020. This will help researchers to understand the current research situation, research trends and research hotspots in this field. This paper uses bibliometrics to examine publications in the field of ARB from 2010 to 2020 that were retrieved from the Web of Science (WOS). Our study performed a statistical analysis of the countries, institutions, journals, authors, research areas, author keywords, Essential Science Indicators (ESI) highly cited papers, and ESI hotspots papers to provide an overview of the ARB field as well as research trends, research hotspots, and future research directions in the field. The results showed that the number of related studies is increasing year by year; the USA is most published in the field of ARB; China is the most active in this field in the recent years; the Chinese Acad Sci published the most articles; Sci. Total Environ. published the greatest number of articles; CM Manaia has the most contributions; Environmental Sciences and Ecology is the most popular research area; and "antibiotic resistance," "antibiotics," and "antibiotic resistance genes" were the most frequently occurring author keywords. A citation analysis showed that aquatic environment-related antibiotic resistance is a key research area in this field, while antimicrobial nanomaterial-related research is a recent popular topic.

Storm promotes the dissemination of antibiotic resistome in an urban lagoon through enhancing bio-interactions

Antibiotic-resistance genes (ARGs) and resistant bacteria (ARB) are abundant in stormwater that could cause serious infections, posing a potential threat to public health. However, there is no inference about how stormwater contributes to ARG profiles as well as the dynamic interplay between ARGs and bacteria via vertical gene transfer (VGT) or horizontal gene transfer (HGT) in urban water ecosystems. In this study, the distribution of ARGs, their host communities, and the source and community assembly process of ARGs were investigated in Yundang Lagoon (China) via high-throughput quantitative PCR, 16S rRNA gene amplicon sequencing, and application of SourceTracker before, after and recovering from an extreme precipitation event (132.1 mm). The abundance of ARGs and mobile genetic elements (MGEs) was the highest one day after precipitation and then decreased 2 days after precipitation and so on. Based on SourceTracker and NMDS analysis, the ARG and bacterial communities in lagoon surface water from one day after precipitation were mainly contributed by the wastewater treatment plant (WWTP) influent and effluent. However, the contribution of WWTP to ARG communities was minor 11 days after the precipitation, suggesting that the storm promoted the ARG levels by introducing the input of ARGs, MGEs, and ARB from point and non-point sources, such as sewer overflow and land-applied manure. Based on a novel microbial network analysis framework, the contribution of positive biological interactions between ARGs and MGEs or bacteria was the highest one day after precipitation, indicating a promoted VGT and HGT for ARG dissemination. The microbial networks deconstructed 11 days after precipitation, suggesting the stormwater practices (e.g., tide gate opening, diversion channels, and pumping) alleviated the spread of ARGs. These results advanced our understanding of the distribution and transport of ARGs associated with their source in urban stormwater runoff.

Humic Lake Exhibits Higher Microbial Functional Gene Diversity and Weaker Gene Interaction Efficiency than a Common Alkaline Lake

Humic lakes (HLs) are special water bodies (high organic matter content, low pH, and low transparency) that are important sources of major greenhouse gases. The knowledge about microbial functional potentials and the interactions among different genes in HL water has been scarcely understood. In this study, we used 16S rRNA gene sequencing and the GeoChip 5.0 to investigate microbial community compositions and functional gene structures in an HL and a reference weakly alkaline lake (RAL). The HL microbial communities showed distinct compositions and functional gene structures than those in the RAL. The functional gene diversity was significantly higher in the HL than in the RAL. Specifically, higher gene relative intensities in carbon and nitrogen fixations, the degradation of various types of carbon, methane oxidation and methanogenesis, ammonification, denitrification, and assimilatory N reduction were observed in the HL samples. By contrast, the metabolic potentials of microorganisms involved in dissimilatory N reduction, phosphorus degradation, and sulfur oxidation were weaker in the HL than in the RAL. Despite higher functional gene diversity, the interaction efficiency among genes (reflected by network geodesic distance and clustering coefficient) might be reduced in the HL. Different functional microbes may develop less interdependent relationships in acquiring nutrients given the high resource availability in the HL. Overall, the enhanced microbial metabolic potentials and less efficient functional interactions might have great consequences on nutrient cycling and greenhouse gas emissions in the HL ecosystem.

Riboflavin- and chlorophyllin-based antimicrobial photoinactivation of Brevundimonas sp. ESA1 biofilms

Some Brevundimonas spp. are globally emerging opportunistic pathogens that can be dangerous to individuals with underlying medical conditions and for those who are immunocompromised. Gram-negative Brevundimonas spp. can form resilient sessile biofilms and are found not only in different confined terrestrial settings (e.g., hospitals) but are also frequently detected in spacecraft which is inhabited by astronauts that can have altered immunity. Therefore, Brevundimonas spp. pose a serious health hazard in different environments, especially in its biofilm form. Conventional antimicrobials applied to disrupt, inactivate, or prevent biofilm formation have limited efficiency and applicability in different closed-loop systems. Therefore, new, effective, and safe biofilm control technologies are in high demand. The present work aimed to investigate antimicrobial photoinactivation (API) of Brevundimonas sp. ESA1 monocultural biofilms mediated by non-toxic, natural photosensitizers such as riboflavin (RF) and chlorophyllin (Chl) with an emphasis of this technology as an example to be safely used in closed-loop systems such as spacecraft. The present study showed that Chl-based API had a bactericidal effect on Brevundimonas sp. ESA1 biofilms at twice the lower irradiation doses than was needed when applying RF-based API. Long-term API based on RF and Chl using 450 nm low irradiance plate has also been studied in this work as a more practically applicable API method. The ability of Brevundimonas sp. ESA1 biofilms to reduce alamarBlue™ and regrowth analysis have revealed that after the applied photoinactivation, bacteria can enter a viable but non-culturable state with no ability to resuscitate in some cases.

Biodegradation of chlortetracycline by Bacillus cereus LZ01: Performance, degradative pathway and possible genes involved

Microbial degradation of chlortetracycline (CTC) is an effective bioremediation method. In the present study, an enrichment technique was used to isolate a Bacillus cereus LZ01 strain capable of effectively degrading CTC from cattle manure. Response surface methodology was used to identify optimized conditions under which strain LZ01 was able to achieve maximal CTC removal (83.58%): temperature of 35.77 °C, solution pH of 7.59, CTC concentration of 57.72 mg/L and microbial inoculum of 0.98%. The antibacterial effect of CTC degradation products on Escherichia coli was investigated by the disk diffusion test, revealing that the products by LZ01 degradation of CTC exhibited lower toxicity than parent compound. Shake flask batch experiments showed that the biodegradation of CTC was a synergistic effect of intracellular and extracellular enzymes, and intracellular enzyme had a better degradation effect on CTC (77.56%). Whole genome sequencing revealed that genes associated with ring-opening hydrolysis, demethylation, deamination and dehydrogenation in strain LZ01 may be involved in the biodegradation of CTC. Subsequent seven possible biodegradation products were identified by LC-MS analyses, and the biodegradation pathways were proposed. Overall, this study provides a theoretical foundation for the characterization and mechanism of CTC degradation in the environment by Bacillus cereus LZ01.

Occurrence and distribution of antibiotic resistant bacteria and genes in the Fuhe urban river and its driving mechanism

Antibiotic resistance genes (ARGs) in urban rivers can affect human health via the food chain and human pathogenic bacteria diffusion. Sediment can be a sink for ARGs, causing second sources of ARG contamination through diffusion. Therefore, we evaluated the effects of total petroleum hydrocarbons (TPHs) and phytoplankton on the distribution of the ARGs in the sediment and water of Fuhe river in Baoding city, China. The ARGs and human pathogenic bacteria in urban river were analyzed, and the phytoplankton and bacterial abundance, TPH, and physicochemical parameters ranked using the partial least squares path modelling (PLS-PM) and aggregated boosted tree (ABT) analysis. The main ARGs in Fuhe river sediment were sulfonamide and tetracycline resistance genes, with sul2 exhibiting the highest level. The main human pathogenic bacteria in the pathogens pool were Clostridium, Bacillus and Burkholderiaceae, with Clostridium demonstrating a positive correlation with SulAfolP01. The PLS-PM analysis confirmed that, among the multiple drivers, water physicochemical factors, TPH, phytoplankton, and heavy metals positively and directly affected the ARG profiles in sediment while sediment heavy metals and bacterial communities did the similar effect. These factors (nutrient factors, heavy metals, and TPH) in water and sediment posed the opposite total effect on ARGs in the sediment, suggesting medium factors should have a conclusive effect on the distribution of ARGs in the sediment. The ABT analysis showed that dissolved oxygen (DO), total nitrogen (TN) and Chlorophyta were the most important factors affecting the ARGs distribution in the water, while TN affected the distribution of the genes in the sediment.

Comparing biotransformation of extracellular polymeric substances (EPS) under aerobic and anoxic conditions: Reactivities, components, and bacterial responses

This study aimed to better understand the transformation behaviors of extracellular polymeric substances (EPS) and their roles in regulating bacterial community in biological wastewater treatment processes. Herein, well-controlled bioassays under aerobic and anoxic conditions were performed to investigate degradation dynamics, composition variations, and bacterial response during EPS transformation. Reactivity continuum modeling showed that organic pools of EPS had continuous reactivity distributions, and most labile organic fraction with a degrading rate >0.1 h^-1 was substantially higher under aerobic (20.47%) than anoxic (2.02%) condition. Rapid degradation of protein-like substances in the initial degradation stage was accompanied by the humification process, as revealed by UV absorption spectroscopy, fluorescence spectroscopy, and size exclusion chromatography with continuous organic carbon detection analysis. The 16S rRNA gene sequencing results showed that the selection effect of EPS in controlling abundant populations during their transformation, e.g., Acinetobacter was enriched, and Candidatus Competibacter was washed out relative to the source community. Furthermore, taxonomic normalized stochasticity ratio-based null model and bacterial ecological network analysis indicated higher relative importance of deterministic process in shaping the EPS-degrading communities under aerobic than anoxic condition, likely explaining the faster EPS biotransformation under aerobic condition. Intriguingly, the keystone populations driving EPS metabolism showed the environmental filtering characteristics (e.g., capable of degrading refractory and aromatic compounds or adapting to harsh environments) and cooperative interactions with the co-occurring species under both conditions. This work is expected to reveal the fates and roles of EPS in wastewater treatment plants extensively.

Conurbation size drives antibiotic resistance along the river

With growing concerns about antibiotic resistance, the tracking of antibiotic resistance genes (ARGs) in urban waterways will facilitate our increased understanding of the impact of urbanization on ARGs dissemination. In the current study, we assessed the ARGs profiles and antibiotic resistome in water samples along the Jiulong River basin, a distance of 250 km, to better understand the impact of anthropogenic activities. A total of 244 ARGs and 12 MGEs were detected from 21 sampling sites. Both relative and absolute abundance of the observed resistome decreased with increasing distance from urban areas. Ordinary least-squares (OLS) regression revealed that both the relative and absolute resistome abundance were positively correlated with city size. The resistome had several inputs and outputs and Fast Expectation Maximization Microbial Source Tracking (FEAST), suggested that the majority of the antibiotic resistome originated from anthropogenic activities. A total of 8 ARGs and 20 microbial OTUs were considered as biomarkers that differentiated the location of sampling sites. Bacterial communities were significantly correlated with ARGs according to Procrustes analysis and Mantel test, which was also supported by a co-occurrence network. Variation partitioning analysis revealed that ARG profiles were driven by multiple factors. Although antibiotic resistome abundance significantly increased near urban conurbations, overall resistome abundance decreased as the river flowed downstream. Our study highlights the effect of conurbation size on antibiotic resistance profiles within the river basin and the potential resilience of rivers to recover from ARGs contamination.

Ag-TiO2/biofilm/nitrate interface enhanced visible light-assisted biodegradation of tetracycline: The key role of nitrate as the electron accepter

Due to the pivotal role of Ag-TiO₂/biofilm/nitrate interface, enhanced visible light-assisted biodegradation of tetracycline (TC) in anoxic system was realized through both batch experiment and long-term operation in this study. The results of the batch experiment elucidated that 50 mg L^-1 TC could be completely removed within 10 h in Ag-TiO₂/biofilm/nitrate system. The continuous flow experiment was operated for 75 d to evaluate the performance and stability of Ag-TiO₂/biofilm/nitrate system. TC removal efficiency in Ag-TiO₂/biofilm/nitrate system was as high as 92.4 ± 1.6% at influent TC concentration of 50 mg L^-1 TC and hydraulic retention time (HRT) of 10 h, which would be attributed to the promoted separation of photoholes and photoelectrons at the presence of nitrate as electron acceptor. Facilitated electron transfer between semiconductor and biofilm was beneficial for enhancing TC biodegradation, thus lowering toxicity of intermediate products and promoting microbial activity. Moreover, the species related to TC biodegradation (Rhodopseudomonas, Phreatobacter and Stenotrophomonas), denitrification (Thauera) and electron transfer (Delftia) were enriched at Ag-TiO₂/biofilm/nitrate interface. Besides, a possible mechanism involved in enhanced TC degradation and nitrogen removal at Ag-TiO₂/biofilm/nitrate interface was proposed. This study provided a novel and promising strategy to enhance recalcitrant TC removal from industrial wastewater.

Antimicrobial Susceptibility, and Molecular Characterization of Staphylococcus aureus Isolated From Different Raw Milk Samples in China

Staphylococcus aureus (S. aureus) is one of the main pathogens in different raw milk and dairy products, which may lead to economic losses. Staphylococcus aureus is a significant and costly public health concern because it may enter the human food chain and contaminate milk causing foodborne illness. This study aimed to investigate the prevalence, antimicrobial susceptibility and virulence genes of S. aureus in raw milks. In total, 125 raw milk samples collected from goat (n = 50), buffalo (n = 25), camel (n = 25), and yak (n = 25) were collected from 5 provinces in China in 2016. Out of 125 samples, 36 (28.8%) S. aureus were isolated (16 from goat, 9 from buffalo, 6 from camel, and 5 from yak). Out of 36 S. aureus, 26 strains (26/36, 72.2%) showed antibiotics resistance, and 6 strains isolated from goats were identified as methicillin-resistant S. aureus (MRSA). The antimicrobial resistance against Penicillin G, tetracycline and gentamicin was 50% (18/36), 41.7% (15/36), and 36.1% (13/36), respectively. 19 S. aureus (52.8%) were considered as multidrug resistant. The highest prevalence of resistant S. aureus was observed in goat milk (13/36, 36.1%). Among the 36 strains, 16 isolates harbored three or more resistant genes. The resistance genes were detected in 25 S. aureus, including 13 strains in goat, 5 strains in buffalo, 4 strains in camel, and 3 strains in yak. Among the 26 resistant strains, 61.5% of isolates harbored three or more resistant genes. The resistance genes were detected in 25 S. aureus, including 13 strains in goat milk, 5 strains in buffalo milk, 4 strains in camel milk, and 3 strains in yak milk. The most predominant resistance genes were blaZ (18/26, 69.2%), aac6′-aph2″ (13/26, 50.0%), and tet(M) (10/26, 38.5%). The mecA, ant(6)-Ia and fexA gene were only detected in S. aureus from goat milk. The most predominant toxin gene were sec (8/26, 30.8%). The majority of S. aureus were multidrug resistant and carried multiple virulence genes, which may pose potential risk to public health. Our findings indicated that the prevalence and antimicrobial resistance of S. aureus was a serious concern in different raw milks in China, especially goat milks.

Occurrence of antibiotics in waters, removal by microalgae-based systems, and their toxicological effects: A review

Global antibiotics consumption has been on the rise, leading to increased antibiotics release into the environment, which threatens public health by selecting for antibiotic resistant bacteria and resistance genes, and may endanger the entire ecosystem by impairing primary production. Conventional bacteria-based treatment methods are only moderately effective in antibiotics removal, while abiotic approaches such as advanced oxidation and adsorption are costly and energy/chemical intensive, and may cause secondary pollution. Considered as a promising alternative, microalgae-based technology requires no extra chemical addition, and can realize tremendous CO₂ mitigation accompanying growth related pollutants removal. Previous studies on microalgae-based antibiotics removal, however, focused more on the removal performances than on the removal mechanisms, and few studies have concerned the toxicity of antibiotics to microalgae during the treatment process. Yet understanding the removal mechanisms can be of great help for targeted microalgae-based antibiotics removal performances improvement. Moreover, most of the removal and toxicity studies were carried out using environment-irrelevant high concentrations of antibiotics, leading to reduced guidance for real-world situations. Integrating the two research fields can be helpful for both improving antibiotics removal and avoiding toxicological effects to primary producers by the residual pollutants. This study, therefore, aims to build a link connecting the occurrence of antibiotics in the aquatic environment, the removal of antibiotics by microalgae-based processes, and the toxicity of antibiotics to microalgae. Distribution of various categories of antibiotics in different water environments were summarized, together with the antibiotics removal mechanisms and performances in microalgae-based systems, and the toxicological mechanisms and toxicity of antibiotics to microalgae after either short-term or long-term exposure. Current research gaps and future prospects were also analyzed. The review could provide much valuable information to the related fields, and provoke interesting thoughts on integrating microalgae-based antibiotics removal research and toxicity research on the basis of environmentally relevant concentrations.

Polystyrene nanoplastics change the functional traits of biofilm communities in freshwater environment revealed by GeoChip 5.0

There is an increasing concern regarding the potential effects of nanoplastics (NPs) on freshwater ecosystems. Considering the functional values of biofilms in freshwater, knowledge on whether and to what extent NPs can influence the ecosystem processes of biofilms were still limited. Herein, the freshwater biofilms cultured in lab were exposed to 100 nm polystyrene NPs (PS-NPs) of different dosages (1 and 10 mg/L) for 14 days. Confocal laser scanning microscope observation indicated that biofilms were dominated by filamentous, and spiral algae species and the intensity of extracellular polymeric substances increased under PS-NPs exposure. GeoChip 5.0 analysis revealed that PS-NPs exposure triggered a significant increase in functional genes α diversity (p < 0.05) and altered biofilms' functional structure. Furthermore, the abundance of genes involved in the total carbon and nitrogen cycling were increased under PS-NPs exposure. The abundance of nitrogen fixation genes experienced the most pronounced increase (24.4%) under 1 mg/L PS-NPs treatment, consistent with the increase of ammonium in overlying water. Whereas antibiotic resistance genes and those related to photosynthetic pigments production were suppressed. These results provided direct evidence for PS-NPs' effects on the biofilm functions in terms of biogeochemical cycling, improving our understanding of the potentials of NPs on freshwater ecosystems.

Distribution characteristics of antibiotic resistance bacteria and related genes in urban recreational lakes replenished by different supplementary water source

The distribution characteristics of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in urban recreational water from different water-supply sources might be different. In this study, water samples were collected to detect the antibiotic resistance of heterotrophic bacteria to five antibiotics, and the content, phenotype, gene type and species distribution of resistant bacteria were analyzed. The results showed that the changes of bacteria resistance rate in two lakes to five kinds of antibiotics were synchronous with time, and it would reach its maximum in autumn. The detection of ARGs and int I in 80 resistance strains showed that the detection rate of tetG, tetA and int I was high. Here, 51.25% of the bacteria were doubly resistant to AMP-CTX. The 80 isolate strains were of nine genera and 19 species, among which Bacillus cereus, Escherichia coli, Aeromonas veronii, Aeromonas caviae and Raoultella ornithinolytica were the common ARB species in two lakes. Correlation analysis showed that the water temperature was significantly correlated with the content of ARB in sulfamethoxazole (SMZ) and cefotaxime (CTX) (p < 0.05), and the total phosphorus (TP) in FQ lake was significantly correlated with the content of AMP-resistant bacteria (p < 0.05), while there were no other correlations between the changes of other water quality indexes and the content of ARB (p > 0.05).

Diversity and distribution of antibiotic resistance genes associated with road sediments transported in urban stormwater runoff

Recently, increasing attention has been paid to antibiotic resistance genes (ARGs) in urban stormwater runoff. However, there were little data on the diversity and distribution of ARGs associated with road sediments transported in runoff. The investigation of ARGs diversity showed that sulfonamide resistance genes (sul2 and sul3) occupied 61.7%-82.3% of total ARGs in runoff. The analysis of ARGs distribution in particulate matter (PM) implied that both tetQ and trbC existed mainly in PM with size of 150-300 μm, but other ARGs and mobile genetic elements (MGEs) were dominant in PM with size <75 μm. The discussion of potential hosts indicated that target genes (ermF, blaOXA1/blaOXA30, ermC, qnrA, sul2, tnpA-01, intI2, tetW, intI1, sul3, trbC) had the strongest subordinate relationship with Proteobacteria at phylum level and Enterobacter at genus level. The effect evaluation of ARGs distribution suggested that 13 kinds of ARGs were positively correlated with Pr/PS and Zeta potential, resulting in the more ARGs in PM with smaller size (<75 μm).

Fecal pollution mediates the dominance of stochastic assembly of antibiotic resistome in an urban lagoon (Yundang lagoon), China

Sewage and fecal pollution cause antibiotic resistance genes (ARGs) pollution in urban lagoons. Seasonality also affects ARG dynamics. However, knowledge of factors controlling ARG community assembly across seasons is still limited. Here, we revealed the seasonal variation of ARGs and depict the underlying assembly processes and drivers via high-throughput quantitative PCR in an urban lagoon, China. A higher richness and abundance of ARGs were observed in summer and winter compared to spring and fall (Kruskal-Wallis test, P < 0.05). Both ARG and prokaryotic communities were mainly governed by stochastic processes, however, these processes drove ARGs and prokaryotes differently across seasons. Stochastic processes played a more dominant role in shaping ARG communities in summer (average stochasticity: 83%) and winter (75%), resulting in a stable antibiotic resistome. However, no such seasonal pattern of stochastic processes was determined for prokaryotes, indicating a decoupling of the assembly process of ARGs and prokaryotes. Moreover, fecal microorganisms (e.g., Bacteroidetes and Faecalibacterium) mediated the stochastic processes of ARG profiles, via enhancement of prokaryotic biomass and mobile genetic element abundances. The tnpA-07 transposase was the key for the horizontal gene transfer. These findings will enhance our understanding of how fecal pollution shapes ARG community assembly in urban lagoons.

Anaerobic condition induces a viable but nonculturable state of the PCB-degrading Bacteria Rhodococcus biphenylivorans TG9

Significant microbial removal of highly chlorinated polychlorinated biphenyls (PCBs) requires the cooperation of anaerobic and aerobic bacteria. During the sequencing process of anaerobic dechlorination and aerobic degradation of PCBs, aerobic degrading bacteria have to undergo anaerobic stress. However, the survival strategy of aerobic degrading bacteria under anaerobic condition is not well-understood. In this study, the culturable cells of Rhodococcus biphenylivorans TG9 decreased from 10⁸ CFU/mL to values below the detection limit after 60 days of anaerobic stress while the viable cells remained 10⁵-10⁶ cells/mL, indicating that anaerobic condition induced TG9 entering into the viable but nonculturable (VBNC) state. Cell resuscitation was observed when oxygen was supplied further confirming the VBNC state of TG9. The results of single-cell Raman spectroscopy combined with heavy water indicated the significant decrease of metabolic activity after TG9 entering into the VBNC state. Additionally, the degradation ability of TG9 in the VBNC state was also significantly reduced, while it recovered after resuscitation. Our research proved that entering into the VBNC state is a survival strategy of TG9 under anaerobic conditions, and the limited culturability and degrading capacity could be overcome by resuscitation. The present study provides new insights for improving the remediation efficiency of PCBs contamination.

Combination of bacitracin-based flocculant and surface enhanced Raman scattering labels for flocculation, identification and sterilization of multiple bacteria in water treatment

Bacteria, especially antibiotic-resistant bacteria, in water threaten public health in countries. Simultaneous flocculation, sterilization and identification of bacteria are great challenge in water treatment. Herein we presented a three-in-one compound through combining a novel Bacitracin-based flocculant (B-g-PAMDAC) and surface enhanced Raman scattering (SERS) labels, the modified Au@AgNPs using graphene oxide (GO) and 4-mercaptophenylboronic acid (4-MPBA). B-g-PAMDAC with bactericidal groups and microblock structure was synthesized via copolymerization and self-assembly. Its functional groups and microblock structure contributed to the excellent performance in flocculation of bacteria. 4-MPBA as bacterial capture bound to the bacterial cell membrane and contributed to recognition of bacteria in flocculation. Bacteria aggregating around Au@AgNPs resulted in abundant "hot spots" and strong Raman signals. SERS labels obviously improved the sensitivity, accuracy and stability of bacteria identification even at low bacterial concentration of 1 × 10³ CFU mL^-1. They presented distinct fingerprints of bacteria, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus and Enterococcus faecalis, in Raman mappings. Bacitracin improved sterilization efficiency of B-g-PAMDAC in four bacteria treatment in terms of sterilization rate and time. β-galactosidase and respiratory activity of bacteria revealed sterilization mechanism of B-g-PAMDAC that changed permeability of cell membrane before it reduced the respiration activity of bacteria and ruptured cell wall.

Hydrometeorological Influence on Antibiotic-Resistance Genes (ARGs) and Bacterial Community at a Recreational Beach in Korea

We investigated the occurrence and distribution of antibiotic-resistance genes (ARGs) and the composition of a bacterial community under conditions of rainfall on a recreational beach in Korea. Seawater samples, collected every 1‒5 hours in June 2018 and May 2019, were analyzed using quantitative real-time polymerase chain reaction and next-generation sequencing. We found a substantial influence of rainfall and tidal levels on the relative abundance of total ARGs and bacterial operational taxonomic units (OTUs), which showed 1.9 × 10³ and 1.1 × 10¹ fold increases, respectively. In particular, the elevated levels of ARGs were maintained for up to 32 hours after rainfall. An increased abundance of sewage-related ARGs and bacterial OTUs suggested that combined sewer overflow (CSO) may be the major factor contributing to the increase in the number and diversity of ARGs and related bacterial communities. Network analysis of ARGs and OTUs indicated that, at the genus level, Acinetobacter, Pseudomonas, and Prevotella were the main potential pathogens carrying the observed ARGs in the recreational seawater. Overall, these findings highlight the potential threat to public health on beaches, and indicate the requirement for more adequate monitoring, with greater efforts to mitigate the propagation of ARGs arising from CSOs.

Antibiotics and antibiotic resistant genes (ARGs) in groundwater: A global review on dissemination, sources, interactions, environmental and human health risks

The discovery and evolution of antibiotics for humans and animals are among the most significant milestones of the 20th century. However, antibiotics play a significant role in the induction and dissemination of antibiotic resistance genes (ARGs) in groundwater that has recently become the primary environmental concern. They are administrated to humans and animals on a large scale and are persistent in the environment. Long term impacts of antibiotics in the ecological environment are not still clearly understood, and their occurrence and consequences have become an important research topic worldwide. The hotspot reservoirs of antibiotics and ARGs include medical facilities, livestock farming, aquaculture, landfills, on-site sanitation systems, sewage, and wastewater treatment plants. Our meta-analysis demonstrated that antibiotics, including ciprofloxacin, sulfamethoxazole, erythromycin, and tetracycline were found at high concentrations while sulfonamide and tetracycline ARGs were more prevalent in groundwater. Moreover, the highest reported concentrations of targeted antibiotics were used to calculate hazard quotient (HQ) and risk quotient (RQ) in global groundwater bodies to estimate environmental and human health risks, respectively. Due to limited available ecotoxicity data, RQ and HQ can only be calculated for a few antibiotics in groundwater. The risk assessment of antibiotics demonstrated that antibiotics with their current groundwater levels pose no human health risks, whereas only ciprofloxacin, erythromycin, flumequine, and sulfamethoxazole revealed moderate to low risks to aquatic species. The occurrence of ARGs and antibiotic resistant bacteria (ARBs) in groundwater is also not likely to pose human health risk but consumption of groundwater contaminated with ARGs and ARBs might contribute to the development of antibiotic resistance in humans. The present review also sheds light on the relationship between ARGs, antibiotics, microbial communities, and environmental factors in groundwater, and reported a significant correlation between them. It also addresses prospects for future outlooks into further areas of relevant research.

Prevalence of antibiotic resistance and virulence genes in the biofilms from an aquifer recharged with stormwater

An improved understanding of the diversity and composition of microbial communities carrying antibiotic resistance genes (ARGs) and virulence genes (VGs) in aquifers recharged with stormwater is essential to comprehend potential human health risks from water reuse. A high-throughput functional gene array was used to study the prevalence of ARGs and VGs in aquifer biofilms (n = 27) taken from three boreholes over three months. Bacterial genera annotated as opportunistic pathogens such as Aeromonas, Burkholderia, Pseudomonas, Shewanella, and Vibrio were ubiquitous and abundant in all biofilms. Bacteria from clinically relevant genera, Campylobacter, Enterobacter, Klebsiella, Mycobacterium, Mycoplasma, and Salmonella were detected in biofilms. The mean travel time of stormwater from the injection well to P1 and P3 boreholes was 260 and 360 days respectively. The presence of ARGs and VGs in the biofilms from these boreholes suggest a high spatial movement of ARGs and VGs in the aquifer. The ARGs with the highest abundance were small multidrug resistance efflux pumps (SMR) and multidrug efflux (Mex) followed by β-lactamase C genes. β- lactamase C encoding genes were primarily detected in Enterobacteriaceae, Pseudomonadaceae, Bacillaceae, and Rhodobacteraceae families. The VGs encoding siderophores, including aerobactin (iro and iuc genes), followed by pilin, hemolysin, and type III secretion were ubiquitous. Canonical correspondence analysis suggested that Total Organic Carbon (TOC), Dissolved Organic Carbon (DOC), turbidity, and Fe concentration has a significant impact on the microbial community structure of bacteria carrying ARGs and VGs. Post abstraction treatment of groundwater may be prudent to improve water security and reduce potential health risks.

Differential responses of stream water and bed sediment microbial communities to watershed degradation

The importance of microbial communities in the function of lotic ecosystems is unequivocal. However, traditional watershed studies on biodiversity have mostly focused on benthic macroinvertebrates, macroalgae and fish assemblages. Here, we investigated the diversity and interaction patterns of microbial communities in water and bed sediment of streams impacted by intensive watershed activities versus streams with relatively pristine conditions via next-generation sequencing of 16S rRNA amplicons using Illumina HiSeq platform. Both water and sediment microbial communities at forested sites had higher mean alpha-diversity than developed sites. Although microbial alpha-diversity indices were generally higher in bed sediment than water, they were comparable at forested sites. In addition, losses of taxa important in nitrogen cycle were evident particularly in bed sediment of developed sites. Interactions among microorganisms visualized by microbial network were more complex at forested sites versus developed sites, with more keystone taxa predominantly from sediment. Together, these findings suggest stream water and bed sediment microbial communities may be affected by watershed disturbances in distinctive ways, and losses of important functional microbial players and keystone taxa in bed sediment may result in decline of ecosystem functions and services. Therefore, cautions should be taken when implementing remediation strategies such as sediment dredging, and reseeding contaminated sites with key microbial players may catalyze the recovery of ecosystems.

Research and Technological Advances Regarding the Study of the Spread of Antimicrobial Resistance Genes and Antimicrobial-Resistant Bacteria Related to Animal Husbandry

The extensive use of antimicrobials in animal farms poses serious safety hazards to both the environment and public health, and this trend is likely to continue. Antimicrobial resistance genes (ARGs) are a class of emerging pollutants that are difficult to remove once introduced. Understanding the environmental transfer of antimicrobial-resistant bacteria (ARB) and ARGs is pivotal for creating control measures. In this review, we summarize the research progress on the spread and detection of ARB and ARG pollution related to animal husbandry. Molecular methods such as high-throughput sequencing have greatly enriched the information about ARB communities. However, it remains challenging to delineate mechanisms regarding ARG induction, transmission, and tempo-spatial changes in the whole process, from animal husbandry to multiple ecosystems. As a result, future research should be more focused on the mechanisms of ARG induction, transmission, and control. We also expect that future research will rely more heavily on metagenomic -analysis, metatranscriptomic sequencing, and multi-omics technologies

Simultaneous debromination and mineralization of bromophenol in an up-flow electricity-stimulated anaerobic system

Due to highly recalcitrant and toxicological nature of halogenated organic compounds, conventional anaerobic dehalogenation is often limited by low removal rate and poor process stability. Besides, the reduction intermediates or products formed during dehalogenation process, which are still toxic, required further energy-intensive aerobic post-treatment. In this study, an up-flow electricity-stimulated anaerobic system (ESAS) was developed by installing cathode underneath and anode above to realize simultaneous anaerobic debromination and mineralization of 4-bromophenol (4-BP). When cathode potential was -600 mV, high TOC removal efficiency (98.78 ± 0.96%), complete removal of 4-BP and phenol could be achieved at 4-BP loading rate of 0.58 mol m^-3 d^-1, suggesting debrominated product of 4-BP from cathode (i.e., phenol) would be utilized as the fuel by the bioanode of ESAS. Under high 4-BP loading rate (2.32 mol m^-3 d^-1) and low electron donor dosage (4.88 mM), 4-BP could be completely removed at acetate usage ratio as low as 4.21 ± 1.42 mol acetate mol^-1 4-BP removal in ESAS, whereas only 13.45 ± 1.38% of 4-BP could be removed at acetate usage ratio as high as 31.28 ± 3.38 mol acetate mol^-1 4-BP removal in control reactor. Besides, electrical stimulation distinctly facilitated the growth of various autotrophic dehalogenation species, phenol degradation related species, fermentative species, homoacetogens and electrochemically active species in ESAS. Moreover, based on the identified intermediates and the bacterial taxonomic analysis, possible metabolism mechanism involved in enhanced anaerobic debromination and mineralization of 4-BP in ESAS was proposed.

Antibiotic resistance in urban runoff

Aquatic ecosystems subjected to anthropogenic pressures are places of rapid evolution of microbial communities and likely hotspots for selection and emergence of antibiotic resistant bacteria. In urban settings, water quality and the risk of infection are generally assessed in sewers and in effluents of wastewater treatment plants. Physical and chemical parameters as well as the presence of antibiotics, antibiotic-resistant bacteria and genes of resistance are driven by urban activities, with adverse effects on aquatic ecosystems. In this paper we review the environmental pressures exerted on bacterial communities in urban runoff waters and discuss the impact of these settings on antibiotic resistance. Considering the worrisome epidemiology of infectious diseases and estimated mortality due to antimicrobial resistance in the coming decades, there is an urgent need to identify all environmental reservoirs of resistant bacteria and resistance genes to complete our knowledge of the epidemiological cycle and of the dynamics of urban antibiotic resistance.

Widespread detection of antibiotic-resistant bacteria from natural aquatic environments in southern Ontario

To elucidate how widespread antibiotic resistance is in the surface water environment, we studied the prevalence of antibiotic resistance bacteria at four locations in southern Ontario. We found that the percentage of bacteria resistant to the antibiotic tetracycline was higher at the river site, which flows through agricultural land, and lower at the lake sites. A total of 225 colonies were selected for further testing of antibiotic disc susceptibility to eight different antibiotics to calculate the multiple antibiotic resistance (MAR) score and the antibiotic resistance index for each site. Although the isolates from the lake site outside the city displayed resistance to fewer antibiotics, their MAR scores were not significantly different from that of the lake sites adjacent to urban beaches, showing that MAR was widespread in the natural water environments tested. Isolation of colonies under selection pressure to tetracycline was found to have a significant effect on the likelihood that the isolates would contain multiple resistance traits for other antibiotics. Identification of isolates selected on tetracycline was compared with that of isolates that were sensitive to tetracycline, and the community composition was found to be distinctly different, although isolates from the genera Chryseobacterium, Pseudomonas, and Stenotrophomonas were found in both communities.

Occurrence of antibiotic resistance genes and bacterial pathogens in water and sediment in urban recreational water

The emergence and prevalence of antibiotic resistance genes (ARGs) and pathogens in the environment are serious global health concern. However, information about the occurrence of ARGs and pathogens in recreational water is still limited. Accordingly, we investigated the occurrence of six ARGs and human pathogens in three recreational lakes, and the correlations between ARGs and one mobile genetic element (intI1) were analyzed. The quantitative PCR results showed that the concentration of ARGs ranged from 4.58 × 10⁰ to 5.0 × 10⁵ copies/mL in water and from 5.78 × 10³ to 5.89 × 10⁸ copies/g dry weight (dw) in sediment. Sul1 exhibited the highest level among the five quantifiable ARGs. The concentrations of sul1, bla_-TEM, and tetX exhibited significant positive correlations with intI1 (p < 0.05), indicating that intI1 may be involved in their proliferation. The detection frequencies of ARGs ranged from 75%-100%, indicating the prevalence of these risks in this region. The concentration of Escherichia coli, Aeromonas spp., Mycobacterium avium, Pseudomonas aeruginosa, and Salmonella enterica ranged from 10³ to 10⁵ copies/100 mL in water and 10⁴-10⁶ copies/g dw in sediment. In total, 25% of the samples harbored all pathogen genes, indicating the prevalence of these pathogens in recreational lakes. Furthermore, the next-generation sequencing results showed that 68 genera of pathogens were present, among which Aeromonas, Mycobacterium, and Pseudomonas were the dominant ones in this region, posing a considerable potential health risk to public health. Overall, the widespread distribution of ARGs and pathogens underscores the need to better monitor and mitigate their propagation in recreational lakes and the associated risks to human health.

Monitoring Antimicrobial Resistance Dissemination in Aquatic Systems

This special issue on Antimicrobial Resistance in Environmental Waters features 11 articles on monitoring and surveillance of antimicrobial resistance (AMR) in natural aquatic systems (reservoirs, rivers), and effluent discharge from water treatment plants to assess the effectiveness of AMR removal and resulting loads in treated waters. The occurrence and distribution of antimicrobials, antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) was determined by utilizing a variety of techniques including liquid chromatography—mass spectrometry in tandem (LC-MS/MS), traditional culturing, antibiotic susceptibility testing (AST), molecular and OMIC approaches. Some of the key elements of AMR studies presented in this special issue highlight the underlying drivers of AMR contamination in the environment and evaluation of the hazard imposed on aquatic organisms in receiving environments through ecological risk assessments. As described in this issue, screening antimicrobial peptide (AMP) libraries for biofilm disruption and antimicrobial candidates are promising avenues for the development of new treatment options to eradicate resistance. This editorial puts into perspective the current AMR problem in the environment and potential new methods which could be applied to surveillance and monitoring efforts.

Diversity of potential antibiotic-resistant bacterial pathogens and the effect of suspended particles on the spread of antibiotic resistance in urban recreational water

Evidence of the increasing incidence of antibiotic resistance in watersheds has attracted worldwide attention. Limited in formation is available on the occurrences of health-related antibiotic-resistant bacterial pathogens (ARBPs) in recreational waters. The effects of certain environmental factors (e.g., suspended particles) on the spread of resistance also has not been characterized to date. In this study, a combination of culture and molecular methods was employed to comprehensively investigate the patterns of microbial resistance to representative antibiotics in samples from three recreational lakes in Beijing. The antibiotic resistance index (ARI) based on the gradient concentration assay revealed that samples showed high resistance to penicillin-G, moderate resistance to ampicillin, vancomycin and erythromycin and low resistance to ceftriaxone, gentamycin, tetracycline and chloramphenicol. Antibiotic-resistant bacteria (ARB) were cultured and collected, and the diversity of potential ARBP species was further explored using next-generation sequencing (NGS). The results showed that most of the identified ARBPs were environmental opportunistic pathogens with emerging clinical concerns, e.g., the multidrug-resistant Acinetobacter junii. Furthermore, particle-attached (PA) fractions presented higher ARI values than free-floating (FL) fractions did, indicating that the PA fractions were more resistant to selected antibiotics. And the NGS results revealed that the PA fractions showed higher similarity in the screened ARB community compositions in comparison with the FL fractions, primarily due to a protective effect provided by the particles. Accordingly, ARBPs could persist for a longer time in protective particle matrices. However, quantification of antibiotic-resistant genes (ARGs) by qPCR showed no significant abundance differences between the two fractions. Overall, these findings suggest a potential health risk from the prevalence of ARBPs in recreational waters and provides a better understanding of the contribution of particles in the spread of antibiotic resistance in aquatic systems, with implications for the control of excessive suspended particles by water management.

Removal of contaminants of emerging concern (CECs) and antibiotic resistant bacteria in urban wastewater using UVA/TiO2/H2O2 photocatalysis

The dispersion of pollutants and proliferation of antibiotic resistant bacteria in the aquatic environment are an emerging health concern worldwide. In this sense, it is essential to develop new technologies to increase the quality of wastewater treatment, which is spread throughout the environment. The present study has demonstrated evidence of the existence of antibiotic and mercury-resistant bacteria in the aquatic environment. The application of heterogeneous photocatalysis with UVA/TiO₂ P25 slurry (200 mg L^-1), UVA/TiO₂-immobilized, and UVA/TiO₂-immobilized/H₂O₂ were evaluated for the simultaneous elimination of a mixture of contaminants of emerging concern (acetamiprid (ACP), imazalil (IMZ) and bisphenol A (BPA)) and inactivation of antibiotic and mercury-resistant bacteria (Pseudomonas aeruginosa and Bacillus subtilis). UVA/TiO₂-immobilized/H₂O₂ increased the inactivation and elimination of the contaminants. After the combined treatment, the mixture of BPA, IMZ and ACP decreased 62%, 21% and <5%, respectively, after 300 min at 13.10 kJ L^-1 of accumulated UV energy. The Pseudomonas aeruginosa strain was inactivated after 120 min using 5.24 kJ L^-1 of accumulated UV energy, whereas the Bacillus subtilis strain was shown to be extremely resistant, with a capacity to develop mechanisms to avoid the oxidation process.

Tracking antibiotic resistance gene pollution from different sources using machine-learning classification

BACKGROUND

Antimicrobial resistance (AMR) has been a worldwide public health concern. Current widespread AMR pollution has posed a big challenge in accurately disentangling source-sink relationship, which has been further confounded by point and non-point sources, as well as endogenous and exogenous cross-reactivity under complicated environmental conditions. Because of insufficient capability in identifying source-sink relationship within a quantitative framework, traditional antibiotic resistance gene (ARG) signatures-based source-tracking methods would hardly be a practical solution.

RESULTS

By combining broad-spectrum ARG profiling with machine-learning classification SourceTracker, here we present a novel way to address the question in the era of high-throughput sequencing. Its potential in extensive application was firstly validated by 656 global-scale samples covering diverse environmental types (e.g., human/animal gut, wastewater, soil, ocean) and broad geographical regions (e.g., China, USA, Europe, Peru). Its potential and limitations in source prediction as well as effect of parameter adjustment were then rigorously evaluated by artificial configurations with representative source proportions. When applying SourceTracker in region-specific analysis, excellent performance was achieved by ARG profiles in two sample types with obvious different source compositions, i.e., influent and effluent of wastewater treatment plant. Two environmental metagenomic datasets of anthropogenic interference gradient further supported its potential in practical application. To complement general-profile-based source tracking in distinguishing continuous gradient pollution, a few generalist and specialist indicator ARGs across ecotypes were identified in this study.

CONCLUSION

We demonstrated for the first time that the developed source-tracking platform when coupling with proper experiment design and efficient metagenomic analysis tools will have significant implications for assessing AMR pollution. Following predicted source contribution status, risk ranking of different sources in ARG dissemination will be possible, thereby paving the way for establishing priority in mitigating ARG spread and designing effective control strategies.

Analysis of extracellular polymeric substances (EPS) and ciprofloxacin-degrading microbial community in the combined Fe-C micro-electrolysis-UBAF process for the elimination of high-level ciprofloxacin

Extracellular polymeric substances (EPS) and ciprofloxacin-degrading microbial community in the combined Fe-C micro-electrolysis and up-flow biological aerated filter (UBAF) process for the treatment of high-level ciprofloxacin (CIP) were analyzed. The research demonstrated a great potential of Fe-C micro-electrolysis-UBAF for the elimination of high-level CIP. Above 90% of CIP removal was achieved through the combined process at 100 mg L^-1 of CIP loading. In UBAF, the pollutants were mainly removed at 0-70 cm heights. Three-dimensional fluorescence spectrum (3D-EEM) was used to characterize the chemical structural of loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) extracted from biofilm sample in UBAF. The results showed that the protein-like substances in LB-EPS and TB-EPS had no clear change in the study. Nevertheless, an obvious release of polysaccharides in EPSs was observed during long-term exposure to CIP, which was considered as a protective response of microbial to CIP toxic. The high-throughput sequencing results revealed that the biodiversity of bacteria community became increasingly rich with gradual ciprofloxacin biodegradation in UBAF. The ciprofloxacin-degrading microbial community was mainly dominated by Proteobacteria and Bacteroidetes. Microorganisms from genera Dechloromonas, Brevundimonas, Flavobacterium, Sphingopyxis and Bosea might take a major role in ciprofloxacin degradation. This study provides deep theoretical guidance for real CIP wastewater treatment.

Characterization of Metagenomes in Urban Aquatic Compartments Reveals High Prevalence of Clinically Relevant Antibiotic Resistance Genes in Wastewaters

The dissemination of antimicrobial resistance (AMR) is an escalating problem and a threat to public health. Comparative metagenomics was used to investigate the occurrence of antibiotic resistant genes (ARGs) in wastewater and urban surface water environments in Singapore. Hospital and municipal wastewater (n = 6) were found to have higher diversity and average abundance of ARGs (303 ARG subtypes, 197,816 x/Gb) compared to treated wastewater effluent (n = 2, 58 ARG subtypes, 2,692 x/Gb) and surface water (n = 5, 35 subtypes, 7,985 x/Gb). A cluster analysis showed that the taxonomic composition of wastewaters was highly similar and had a bacterial community composition enriched in gut bacteria (Bacteroides, Faecalibacterium, Bifidobacterium, Blautia, Roseburia, Ruminococcus), the Enterobacteriaceae group (Klebsiella, Aeromonas, Enterobacter) and opportunistic pathogens (Prevotella, Comamonas, Neisseria). Wastewater, treated effluents and surface waters had a shared resistome of 21 ARGs encoding multidrug resistant efflux pumps or resistance to aminoglycoside, macrolide-lincosamide-streptogramins (MLS), quinolones, sulfonamide, and tetracycline resistance which suggests that these genes are wide spread across different environments. Wastewater had a distinctively higher average abundance of clinically relevant, class A beta-lactamase resistant genes (i.e., blaKPC, blaCTX-M, blaSHV, blaTEM). The wastewaters from clinical isolation wards, in particular, had a exceedingly high levels of blaKPC-2 genes (142,200 x/Gb), encoding for carbapenem resistance. Assembled scaffolds (16 and 30 kbp) from isolation ward wastewater samples indicated this gene was located on a Tn3-based transposon (Tn4401), a mobilization element found in Klebsiella pneumonia plasmids. In the longer scaffold, transposable elements were flanked by a toxin-antitoxin (TA) system and other metal resistant genes that likely increase the persistence, fitness and propagation of the plasmid in the bacterial host under conditions of stress. A few bacterial species (Enterobacter cloacae, Klebsiella pneumoniae, Citrobacter freundii, Pseudomonas aeruginosa) that were cultured from the isolation ward wastewaters on CHROMagar media harbored the blaKPC-2 gene. This suggests that hospital wastewaters derived from clinical specialty wards are hotspots for the spread of AMR. Assembled scaffolds of other mobile genetic elements such as IncQ and IncF plasmids bearing quinolone resistance genes (qnrS1, qnrS2) and the class A beta-lactamase gene (blaTEM-1) were recovered in wastewater samples which may aid the transfer of AMR.

Analysis of the functional gene structure and metabolic potential of microbial community in high arsenic groundwater

Microbial functional potential in high arsenic (As) groundwater ecosystems remains largely unknown. In this study, the microbial community functional composition of nineteen groundwater samples was investigated using a functional gene array (GeoChip 5.0). Samples were divided into low and high As groups based on the clustering analysis of geochemical parameters and microbial functional structures. The results showed that As related genes (arsC, arrA), sulfate related genes (dsrA and dsrB), nitrogen cycling related genes (ureC, amoA, and hzo) and methanogen genes (mcrA, hdrB) in groundwater samples were correlated with As, SO₄^2-, NH₄⁺ or CH₄ concentrations, respectively. Canonical correspondence analysis (CCA) results indicated that some geochemical parameters including As, total organic content, SO₄^2-, NH₄⁺, oxidation-reduction potential (ORP) and pH were important factors shaping the functional microbial community structures. Alkaline and reducing conditions with relatively low SO₄^2-, ORP, and high NH₄⁺, as well as SO₄^2- and Fe reduction and ammonification involved in microbially-mediated geochemical processes could be associated with As enrichment in groundwater. This study provides an overall picture of functional microbial communities in high As groundwater aquifers, and also provides insights into the critical role of microorganisms in As biogeochemical cycling.