The Pseudomonas community in metal-contaminated sediments as revealed by quantitative PCR: a link with metal bioavailability. - Related Documents




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610401.0000The Pseudomonas community in metal-contaminated sediments as revealed by quantitative PCR: a link with metal bioavailability. Pseudomonas bacteria are ubiquitous Gram-negative and aerobic microorganisms that are known to harbor metal resistance mechanisms such as efflux pumps and intracellular redox enzymes. Specific Pseudomonas bacteria have been quantified in some metal-contaminated environments, but the entire Pseudomonas population has been poorly investigated under these conditions, and the link with metal bioavailability was not previously examined. In the present study, quantitative PCR and cell cultivation were used to monitor and characterize the Pseudomonas population at 4 different sediment sites contaminated with various levels of metals. At the same time, total metals and metal bioavailability (as estimated using an HCl 1 m extraction) were measured. It was found that the total level of Pseudomonas, as determined by qPCR using two different genes (oprI and the 16S rRNA gene), was positively and significantly correlated with total and HCl-extractable Cu, Co, Ni, Pb and Zn, with high correlation coefficients (>0.8). Metal-contaminated sediments featured isolates of the Pseudomonas putida, Pseudomonas fluorescens, Pseudomonas lutea and Pseudomonas aeruginosa groups, with other bacterial genera such as Mycobacterium, Klebsiella and Methylobacterium. It is concluded that Pseudomonas bacteria do proliferate in metal-contaminated sediments, but are still part of a complex community.201425102022
610910.9998Studies on arsenic transforming groundwater bacteria and their role in arsenic release from subsurface sediment. Ten different Gram-negative arsenic (As)-resistant and As-transforming bacteria isolated from As-rich groundwater of West Bengal were characterized to assess their role in As mobilization. 16S rRNA gene analysis confirmed the affiliation of these bacteria to genera Achromobacter, Brevundimonas, Rhizobium, Ochrobactrum, and Pseudoxanthomonas. Along with superior As-resistance and As-transformation abilities, the isolates showed broad metabolic capacity in terms of utilizing a variety of electron donors and acceptors (including As) under aerobic and anaerobic conditions, respectively. Arsenic transformation studies performed under various conditions indicated highly efficient As(3+) oxidation or As(5+) reduction kinetics. Genes encoding As(3+) oxidase (aioA), cytosolic As(5+) reductase (arsC), and As(3+) efflux pump (arsB and acr3) were detected within the test isolates. Sequence analyses suggested that As homeostasis genes (particularly arsC, arsB, and acr3) were acquired by most of the bacteria through horizontal gene transfer. A strong correlation between As resistance phenotype and the presence of As(3+) transporter genes was observed. Microcosm study showed that bacterial strain having cytosolic As(5+) reductase property could play important role in mobilizing As (as As(3+)) from subsurface sediment.201424764001
371320.9998Arsenic Pollution and Anaerobic Arsenic Metabolizing Bacteria in Lake Van, the World's Largest Soda Lake. Arsenic is responsible for water pollution in many places around the world and presents a serious health risk for people. Lake Van is the world's largest soda lake, and there are no studies on seasonal arsenic pollution and arsenic-resistant bacteria. We aimed to determine the amount of arsenic in the lake water and sediment, to isolate arsenic-metabolizing anaerobic bacteria and their identification, and determination of arsenic metabolism. Sampling was done from 7.5 m to represent the four seasons. Metal contents were determined by using ICP-MS. Pure cultures were obtained using the Hungate technique. Growth characteristics of the strains were determined at different conditions as well as at arsenate and arsenite concentrations. Molecular studies were also carried out for various resistance genes. Our results showed that Lake Van's total arsenic amount changes seasonally. As a result of 16S rRNA sequencing, it was determined that the isolates were members of 8 genera with arsC resistance genes. In conclusion, to sustain water resources, it is necessary to prevent chemical and microorganism-based pollution. It is thought that the arsenic-resistant bacteria obtained as a result of this study will contribute to the solution of environmental arsenic pollution problems, as they are the first data and provide the necessary basic data for the bioremediation studies of arsenic from contaminated environmental habitats. At the same time, the first data that will contribute to the creation of the seasonal arsenic map of Lake Van are obtained.202236431035
741630.9998Effect of copper and zinc as sulfate or nitrate salts on soil microbiome dynamics and bla(VIM)-positive Pseudomonas aeruginosa survival. The exposure of soil to metals and to antibiotic resistant bacteria may lead to the progressive deterioration of soil quality. The persistence of antibiotic resistant bacteria or antibiotic resistance genes in soil can be influenced by the microbial community or by soil amendments with metal salts. This work assessed the effect of soil amendment with copper and zinc, as sulfate or nitrate salts, on the fate of a carbapenem-resistant (bla(VIM)(+)) hospital effluent isolate of Pseudomonas aeruginosa (strain H1FC49) and on the variations of the microbial community composition. Microcosms with soil aged or not with copper and zinc salts (20 mM), and inoculated with P. aeruginosa H1FC49 were monitored at 0, 7, 14 and/or 30 days, for community composition (16S rRNA gene amplicon) and strain H1FC49 persistence. Data on culturable P. aeruginosa, quantitative PCR of the housekeeping gene ecf, and the presumably acquired genes bla(VIM)(+) and integrase (intI1), and community composition were interpreted based on descriptive statistics and multivariate analysis. P. aeruginosa and the presumably acquired genes, were quantifiable in soil for up to one month, in both metal-amended and non-amended soil. Metal amendments were associated with a significant decrease of bacterial community diversity and richness. The persistence of P. aeruginosa and acquired genes in soils, combined with the adverse effect of metals on the bacterial community, highlight the vulnerability of soil to both types of exogenous contamination.202133773246
385340.9998Co-selection of antibiotic-resistant bacteria in a paddy soil exposed to As(III) contamination with an emphasis on potential pathogens. The increased acquisition of antibiotic resistance by pathogens is a global health concern. The environmental selection of antibiotic resistance can be caused by either antibiotic residues or co-selecting agents such as toxic metal(loid)s. This study explored the potential role of As(III) as a co-selecting driver in the spread of antibiotic resistance in paddy soils. By applying high-throughput sequencing, we found that the diversity and composition of soil microbial communities was significantly altered by As(III) exposure, resulting in an increased proportion of potential pathogens (9.9%) compared to the control soil (0.1%). Meanwhile, a total of 46 As(III)-resistant isolates were obtained from As(III)-exposure soil, among which potential pathogens accounted for 54.3%. These As(III)-resistant bacteria showed a high incidence of resistance to sulfanilamide (100%) and streptomycin (88-93%). The association between antibiotic and As(III) resistances was further investigated in a potentially pathogenic isolate by whole-genome sequencing and a transcription assay. The results showed that As(III) and antibiotic resistance genes might co-occur in a mobile genomic island and be co-regulated by As(III), implying that antibiotic resistance could be co-selected by As(III) via co-resistance and co-regulation mechanisms. Overall, these results suggest that As(III) exposure provides a strong selective pressure for the expansion of soil bacterial resistome.202032302839
610350.9998Culture-dependent study of arsenic-reducing bacteria in deep aquatic sediments of Bengal Delta. Biogeochemical release of soil-bound arsenic (As) governs mobilization of the toxic metalloid into the groundwater. The present study has examined As(V)-reduction ability of bacteria from anoxic aquatic sediments that might contribute to arsenic mobilization in the Bengal Delta. Arsenic-reducing bacteria from deep layers of pond sediment were enriched and isolated in anaerobic environments and As(V) reduction was assessed in culture medium. The pond sediment enrichments harboured As(V)-reducing bacteria belonging to the phyla Firmicutes and Proteobacteria with dominance of Paraclostridium benzoelyticum and P. bifermentans. Among total 17 isolates, the respiratory reductase genes were not detected by the most common primers and only 3 strains had arsenic reductase ArsC gene suggesting involvement of resistance and some unknown mechanisms in As(V) reduction. Presence of high levels of organic matter, As, and As-reducing bacteria might make deep aquatic sediments a hot spot of As mobilization and aquifer contamination.202134482463
740660.9998Relationship between antibiotic resistance genes and metals in residential soil samples from Western Australia. Increasing drug-resistant infections have drawn research interest towards examining environmental bacteria and the discovery that many factors, including elevated metal conditions, contribute to proliferation of antibiotic resistance (AR). This study examined 90 garden soils from Western Australia to evaluate predictions of antibiotic resistance genes from total metal conditions by comparing the concentrations of 12 metals and 13 genes related to tetracycline, beta-lactam and sulphonamide resistance. Relationships existed between metals and genes, but trends varied. All metals, except Se and Co, were related to at least one AR gene in terms of absolute gene numbers, but only Al, Mn and Pb were associated with a higher percentage of soil bacteria exhibiting resistance, which is a possible indicator of population selection. Correlations improved when multiple factors were considered simultaneously in a multiple linear regression model, suggesting the possibility of additive effects occurring. Soil-metal concentrations must be considered when determining risks of AR in the environment and the proliferation of resistance.201727822686
457170.9998Growth of soil bacteria, on penicillin and neomycin, not previously exposed to these antibiotics. There is growing evidence that bacteria, in the natural environment (e.g. the soil), can exhibit naturally occurring resistance/degradation against synthetic antibiotics. Our aim was to assess whether soils, not previously exposed to synthetic antibiotics, contained bacterial strains that were not only antibiotic resistant, but could actually utilize the antibiotics for energy and nutrients. We isolated 19 bacteria from four diverse soils that had the capability of growing on penicillin and neomycin as sole carbon sources up to concentrations of 1000 mg L(-1). The 19 bacterial isolates represent a diverse set of species in the phyla Proteobacteria (84%) and Bacteroidetes (16%). Nine antibiotic resistant genes were detected in the four soils but some of these genes (i.e. tetM, ermB, and sulI) were not detected in the soil isolates indicating the presence of unculturable antibiotic resistant bacteria. Most isolates that could subsist on penicillin or neomycin as sole carbon sources were also resistant to the presence of these two antibiotics and six other antibiotics at concentrations of either 20 or 1000 mg L(-1). The potentially large and diverse pool of antibiotic resistant and degradation genes implies ecological and health impacts yet to be explored and fully understood.201424956077
371280.9998Enumeration and characterization of culturable arsenate resistant bacteria in a large estuary. Arsenic is a toxic element that exists in two major inorganic forms, arsenate and arsenite. A number of bacteria have been shown to resist arsenic exposure, and even more bacteria appear to possess the genes for arsenic resistance. In this study, the numbers of culturable arsenate-resistant bacteria present in water at three coastal sites in the Lake Pontchartrain estuary, Louisiana, was determined. Despite insignificant (less than 1.33 microM) levels of arsenic in this system, 20-50% of the viable count of bacteria showed appreciable arsenate resistance, suggesting that arsenic-resistant bacteria are common and widespread. A diverse array of arsenate-resistant isolates was obtained, with 16S rRNA sequence analysis indicating 37 different bacterial strains, representing six major bacterial groups. Many of these isolates were affiliated with groups of bacteria that have been poorly characterized in terms of arsenic resistance, such as the Betaproteobacteria or Flavobacteria. Some isolates were capable of tolerating very high (> 100 mM) levels of arsenate, although arsenite resistance was generally much lower. The results suggest that arsenic-resistant bacteria are common, even in environments with insignificant arsenic contamination, and that many different groups of aquatic bacteria show appreciable arsenic resistance.200516261862
609990.9997Culture-dependent and independent studies of microbial diversity in highly copper-contaminated Chilean marine sediments. Cultivation and molecular-based approaches were used to study microbial diversity in two Chilean marine sediments contaminated with high (835 ppm) and very high concentrations of copper (1,533 ppm). The diversity of cultivable bacteria resistant to copper was studied at oxic and anoxic conditions, focusing on sulfate-, thiosulfate-, and iron-reducing bacteria. For both sediments, the cultivable bacteria isolated at oxic conditions were mostly affiliated to the genus Bacillus, while at anoxic conditions the majority of the cultivable bacteria found were closely related to members of the genera Desulfovibrio, Sphingomonas, and Virgibacillus. Copper resistance was between 100 and 400 ppm, with the exception of a strain affiliated to members of the genus Desulfuromonas, which was resistant up to 1,000 ppm of copper. In parallel, cloning and sequencing of 16S rRNA was performed to study the total bacterial diversity in the sediments. A weak correlation was observed between the isolated strains and the 16S rRNA operational taxonomic units detected. The presence of copper resistance genes (copA, cusA, and pcoA) was tested for all the strains isolated; only copA was detected in a few isolates, suggesting that other copper resistance mechanisms could be used by the bacteria in those highly copper-contaminated sediments.201322976340
3852100.9997Phenotype profiles and adaptive preference of Acinetobacter johnsonii isolated from Ba River with different environmental backgrounds. Acinetobacter johnsonii is a potentially opportunistic pathogen widely distributed in nosocomial and natural environments, but little attention has been paid to this bacillus. Here A. johnsonii strains from Ba River with different pollution levels were isolated. In this study, we found that the increasing anthropogenic contaminants accounted for the emergence of multidrug-resistant (MDR) A. johnsonii strains. Correlation analysis results showed that the resistance phenotype of strains could be generated by co-selection of heavy metals or non-corresponding antibiotics. The whole genome sequence analysis showed that the relative heavy pollution of water selects strains containing more survival-relevant genes. We found that only some genes like bla(OXA-24) were responsible for its corresponding resistance profile. Additionally, the tolerance profiles toward heavy metals also attribute to the expression of efflux pumps rather than corresponding resistance genes. In summary, our finding revealed that the resistance profiles of A. johnsonii could be generated by cross or co-selection of anthropogenic contaminants and mediated by efflux pumps instead of corresponding resistance determinants. Our study also has deep-sight into the adaptive preference of bacteria in natural environments, and contributes to surveillance studies and MDR- A. johnsonii monitoring worldwide.202133639142
3845110.9997A novel microfluidic system enables visualization and analysis of antibiotic resistance gene transfer to activated sludge bacteria in biofilm. Antibiotic resistance genes (ARGs) in environment have become a growing public concern, due to their potential to be obtained by pathogens and their duplication along cell division. Horizontal gene transfer (HGT) was reported to be responsible for ARGs dissemination in microbes, but the HGT feature in environmental biofilm was still unclear due to insufficient assay tools. To address this challenge, we applied a novel microfluidic system to cultivate thin biofilm by continuous supply of nutrients and close contact between cells. Resembling the living state of biofilm in open environment, this chip visualized the transfer of ARG-encoded plasmids RP4 and pKJK5 to the receptors, e.g., activated sludge bacteria. The average plasmid transfer frequency per receptor (T/R) from RP4-hosted Pseudomonas putida KT2440 to activated sludge bacteria was quantified to be 2.5 × 10(-3) via flow cytometry, and T/R for pKJK5-hosted Escherichia coli MG1655 was 8.9 × 10(-3), while the corresponding average frequencies per donor (T/D) were diverse for the two host strains as 4.3 × 10(-3) and 1.4 × 10(-1) respectively. The difference between T/R and T/D was explained by the plasmid transfer kinetics, implying specific purposes of the two calculations. Finally, we collected the transconjugants by fluorescent activated cell sorting and further sequenced their 16S rDNA. Bacteria from phyla Proteobacteria and Firmicutes were found more susceptible to be transconjugants than those from Bacteroidetes. Our work demonstrated that microfluidic system was advantageous in biofilm HGT study, which can provide more insights into environmental ARG control.201829909325
3860120.9997Mobility of antibiotic resistance and its co-occurrence with metal resistance in pathogens under oxidative stress. The bacterial communities are challenged with oxidative stress during their exposure to bactericidal antibiotics, metals, and different levels of dissolved oxygen (DO) encountered in diverse environmental habitats. The frequency of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) co-selection is increased by selective pressure posed by oxidative stress. Hence, study of resistance acquisition is important from an evolutionary perspective. To understand the dependence of oxidative stress on the dissemination of ARGs and MRGs through a pathogenic bacterial population, 12 metagenomes belonging to gut, water and soil habitats were evaluated. The metagenome-wide analysis showed the chicken gut to pose the most diverse pool of ARGs (30.4 ppm) and pathogenic bacteria (Simpson diversity = 0.98). The most common types of resistances found in all the environmental samples were efflux pumps (13.22 ppm) and genes conferring resistance to vancomycin (12.4 ppm), tetracycline (12.1 ppm), or beta-lactam (9.4 ppm) antibiotics. Additionally, limiting DO level in soil was observed to increase the abundance of excision nucleases (uvrA and uvrB), DNA polymerase (polA), catalases (katG), and other oxidative stress response genes (OSGs). This was further evident from major variations occurred in antibiotic efflux genes due to the effect of DO concentration on two human pathogens, namely Salmonella enterica and Shigella sonnei found in all the selected habitats. In conclusion, the microbial community, when challenged with oxidative stress caused by environmental variations in oxygen level, tends to accumulate higher amounts of ARGs with increased dissemination potential through triggering non-lethal mutagenesis. Furthermore, the genetic linkage or co-occurrence of ARGs and MRGs provides evidence for selecting ARGs under high concentrations of heavy metals.202134298350
3711130.9997Characterization of aerobic polycyclic aromatic hydrocarbon-degrading bacteria from Bizerte lagoon sediments, Tunisia. AIMS: To characterize polycyclic aromatic hydrocarbon (PAH)-degrading bacteria from sediments of the Bizerte lagoon, and to determine their ability to resist other pollutants such as antibiotics and heavy metals. METHODS AND RESULTS: More than 100 strains were isolated for their ability to use fluoranthene as the sole carbon and energy source. Most of them showed antibiotic and heavy metal resistance; 20 representative strains were selected for further analysis. 16S rRNA coding sequences analysis showed that the majority of the selected bacteria (75%) were affiliated to the Gammaproteobacteria. The selected strains also utilized high molecular weight PAHs containing up to four benzene rings and showed different profiles of PAH substrate usage suggesting different PAH degradation pathways. These results are consistent with the fact that nah-like genes and idoA-like genes, involved in PAH degradation, were detected in 6 and 1 strains respectively. CONCLUSIONS: The Bizerte lagoon, polluted by many human activities, leads to the co-selection of strains able to cope with multiple contaminants. SIGNIFICANCE AND IMPACT OF THE STUDY: Polluted areas are often characterized by the concomitant presence of organic pollutants, heavy metals and antibiotics. This study is one of the first showing bacterial strains adapted to multiple contaminants, a promising potential for the development of bioremediation processes.200817973912
3859140.9997Co-selection of antibiotic resistance via copper shock loading on bacteria from a drinking water bio-filter. Heavy metal contamination of source water frequently occurred in developing countries as a result of accidents. To address the problems, most of the previous studies have focused on engineering countermeasures. In this study, we investigated the effects of heavy metals, particularly copper, on the development of antibiotic resistance by establishing a copper shock loading test. Results revealed that co-selection occurred rapidly within 6 h. Copper, at the levels of 10 and 100 mg/L, significantly increased bacterial resistance to the antibiotics tested, including rifampin, erythromycin, kanamycin, and a few others. A total of 117 antimicrobial-resistance genes were detected from 12 types of genes, and the relative abundance of most genes (particularly mobile genetic elements intⅠand transposons) was markedly enriched by at least one fold. Furthermore, the copper shock loading altered the bacterial community. Numerous heavy metal and antibiotic resistant strains were screened out and enriched. These strains are expected to enhance the overall level of resistance. More noticeably, the majority of the co-selected antibiotic resistance could sustain for at least 20 h in the absence of copper and antimicrobial drugs. Resistance to vancomycin, erythromycin and lincomycin even could remain for 7 days. The prominent selection pressure by the copper shock loading implies that a real accident most likely poses similar impacts on the water environment. An accidental release of heavy metals would not only cause harm to the ecological environment, but also contribute to the development of bacterial antibiotic resistance. Broader concerns should be raised about the biological risks caused by sudden releases of pollutants by accidents.201829059628
3685150.9997Selective concentration for ciprofloxacin resistance in Escherichia coli grown in complex aquatic bacterial biofilms. There is concern that antibiotics in the environment can select for and enrich bacteria carrying acquired antibiotic resistance genes, thus increasing the potential of those genes to emerge in a clinical context. A critical question for understanding and managing such risks is what levels of antibiotics are needed to select for resistance in complex bacterial communities. Here, we address this question by examining the phenotypic and genotypic profiles of aquatic communities exposed to ciprofloxacin, also evaluating the within-species selection of resistant E. coli in complex communities. The taxonomic composition was significantly altered at ciprofloxacin exposure concentrations down to 1 μg/L. Shotgun metagenomic analysis indicated that mobile quinolone resistance determinants (qnrD, qnrS and qnrB) were enriched as a direct consequence of ciprofloxacin exposure from 1 μg/L or higher. Only at 5-10 μg/L resistant E.coli increased relative to their sensitive counterparts. These resistant E. coli predominantly harbored non-transferrable, chromosomal triple mutations (gyrA S83 L, D87N and parC S80I), which confer high-level resistance. In a controlled experimental setup such as this, we interpret effects on taxonomic composition and enrichment of mobile quinolone resistance genes as relevant indicators of risk. Hence, the lowest observed effect concentration for resistance selection in complex communities by ciprofloxacin was 1 μg/L and the corresponding no observed effect concentration 0.1 μg/L. These findings can be used to define and implement discharge or surface water limits to reduce risks for selection of antibiotic resistance in the environment.201829704804
3688160.9997Functional metagenomic characterization of antibiotic resistance genes in agricultural soils from China. Soil has been regarded as a rich source of antibiotic resistance genes (ARGs) due to the complex microbial community and diverse antibiotic-producing microbes in soil, however, little is known about the ARGs in unculturable bacteria. To investigate the diversity and distribution of ARGs in soil and assess the impact of agricultural practice on the ARGs, we screened soil metagenomic library constructed using DNA from four different agricultural soil for ARGs. We identified 45 clones conferring resistance to minocycline, tetracycline, streptomycin, gentamicin, kanamycin, amikacin, chloramphenicol and rifampicin. The similarity of identified ARGs with the closest protein in GenBank ranged from 26% to 92%, with more than 60% of identified ARGs had low similarity less than 60% at amino acid level. The identified ARGs include aminoglycoside acetyltransferase, aminoglycoside 6-adenyltransferase, ADP-ribosyl transferase, ribosome protection protein, transporters and other antibiotic resistant determinants. The identified ARGs from the soil with manure application account for approximately 70% of the total ARGs in this study, implying that manure amendment may increase the diversity of antibiotic resistance genes in soil bacteria. These results suggest that antibiotic resistance in soil remains unexplored and functional metagenomic approach is powerful in discovering novel ARGs and resistant mechanisms.201424412260
3683170.9997Small and large-scale distribution of four classes of antibiotics in sediment: association with metals and antibiotic resistance genes. Antibiotic chemicals and antibiotic resistance genes enter the environment via wastewater effluents as well as from runoff from agricultural operations. The relative importance of these two sources, however, is largely unknown. The relationship between the concentrations of chemicals and genes requires exploration, for antibiotics in the environment may lead to development or retention of resistance genes by bacteria. The genes that confer resistance to metal toxicity may also be important in antibiotic resistance. In this work, concentrations of 19 antibiotics (using liquid chromatography tandem mass spectrometry), 14 metals (using inductively coupled plasma-mass spectrometry), and 45 metal, antibiotic, and antibiotic-resistance associated genes (using a multiplex, microfluidic quantitative polymerase chain reaction method) were measured in 13 sediment samples from two large rivers as well as along a spatial transect in a wastewater effluent-impacted lake. Nine of the antibiotics were detected in the rivers and 13 were detected in the lake. Sixteen different resistance genes were detected. The surrounding land use and proximity to wastewater treatment plants are important factors in the number and concentrations of antibiotics detected. Correlations among antibiotic chemical concentrations, metal concentrations, and resistance genes occur over short spatial scales in a lake but not over longer distances in major rivers. The observed correlations likely result from the chemicals and resistance genes arising from the same source, and differences in fate and transport over larger scales lead to loss of this relationship.201830043816
7965180.9997Screening and evaluation of heavy metals facilitating antibiotic resistance gene transfer in a sludge bacterial community. Recent growing evidence suggests that heavy metals can stimulate the transfer of antibiotic resistance genes (ARGs) between bacteria. However, most previous studies focused on pure strains, the effect of heavy metals on ARG transfer in bacterial communities, especially in activated sludge, has not been clearly explored. In this study, a high-throughput method, combining computerized incubator (Bioscreen C) and flow cytometry, was developed to evaluate different concentrations of heavy metals influencing ARG transfer in sludge bacteria communities. By using Escherichia coli MG1655 as the donor of broad-host range IncP-1 plasmid pKJK5, it was found that 0.5 mmol/L Pb, 0.1 mmol/L As and 0.005 mmol/L Hg could obviously promote ARG transfer in sludge bacteria communities. Furthermore, mating assays on microfluidic chips also proved higher transfer frequencies in attached communities under the above heavy metal stresses. Transconjugants under Pb, As and Hg stresses were isolated and phylogenetically described. For As and Hg, the dominant genus was Pseudomonas, accounting for 88% and 96%, respectively. While under Pb stress, the genera Aeromonas and Enterobacter were the main transconjugants, accounting for 56% and 32% respectively. Moreover, ABC transporters and Amino acid metabolism, which were related to heavy metal transport and cellular metabolism, were dominant in the prediction of microbial metabolic function of transconjugants. This study can be helpful for risk assessment and control of ARG spreading in WWTPs.201931425984
3704190.9997Antibiotic resistance in bacteria isolated from the deep terrestrial subsurface. Various natural environments have been examined for the presence of antibiotic-resistant bacteria and/or novel resistance mechanisms, but little is known about resistance in the terrestrial deep subsurface. This study examined two deep environments that differ in their known period of isolation from surface environments and the bacteria therein. One hundred fifty-four strains of bacteria were isolated from sediments located 170-259 m below land surface at the US Department of Energy Savannah River Site (SRS) in South Carolina and Hanford Site (HS) in Washington. Analyses of 16S rRNA gene sequences showed that both sets of strains were phylogenetically diverse and could be assigned to several genera in three to four phyla. All of the strains were screened for resistance to 13 antibiotics by plating on selective media and 90% were resistant to at least one antibiotic. Eighty-six percent of the SRS and 62% of the HS strains were resistant to more than one antibiotic. Resistance to nalidixic acid, mupirocin, or ampicillin was noted most frequently. The results indicate that antibiotic resistance is common among subsurface bacteria. The somewhat higher frequencies of resistance and multiple resistance at the SRS may, in part, be due to recent surface influence, such as exposure to antibiotics used in agriculture. However, the HS strains have never been exposed to anthropogenic antibiotics but still had a reasonably high frequency of resistance. Given their long period of isolation from surface influences, it is possible that they possess some novel antibiotic resistance genes and/or resistance mechanisms.200918677528