Genomic Characterization of a Mercury Resistant Arthrobacter sp. H-02-3 Reveals the Presence of Heavy Metal and Antibiotic Resistance Determinants. - Related Documents




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610501.0000Genomic Characterization of a Mercury Resistant Arthrobacter sp. H-02-3 Reveals the Presence of Heavy Metal and Antibiotic Resistance Determinants. Nuclear production and industrial activities led to widespread contamination of the Department of Energy (DOE) managed Savannah River Site (SRS), located in South Carolina, United States. The H-02 wetland system was constructed in 2007 for the treatment of industrial and storm water runoff from the SRS Tritium Facility. Albeit at low levels, mercury (Hg) has been detected in the soils of the H-02 wetland ecosystem. In anoxic sediments, Hg is typically methylated by anaerobic microbiota, forming the highly neurotoxic methylmercury (MeHg), which biomagnifies across food webs. However, in surficial oxic wetland soils, microbially mediated demethylation and/or volatilization processes can transform Hg(2+) into the less toxic Hg(0) form which is released into the atmosphere, thus circumventing MeHg formation. To obtain a deeper understanding on bacterial Hg volatilization, a robust Hg-resistant (HgR) bacteria, called as strain H-02-3 was isolated from the H-02 soils. A draft genome sequence of this strain was obtained at a coverage of 700×, which assembled in 44 contigs with an N50 of 171,569 bp. The genomic size of the strain H-02-3 was 4,708,612 bp with a total number of 4,240 genes; phylogenomic analysis revealed the strain as an Arthrobacter species. Comparative genomics revealed the presence of 1100 unique genes in strain H-02-3, representing 26.7% of the total genome; many identified previously as metal resistance genes (MRGs). Specific to Hg-cycling, the presence of mercuric ion reductase (merA), the organomercurial lyase (merB), and the mercuric resistance operon regulatory protein, were identified. By inference, it can be proposed that the organomercurial lyase facilitates the demethylation of MeHg into Hg(2+) which is then reduced to Hg(0) by MerA in strain H-02-3. Furthermore, gene prediction using resistome analysis of strain H-02-3 revealed the presence of several antibiotic resistance genes (ARGs), that statistically correlated with the presence of metal resistant genes (MRGs), suggesting co-occurrence patterns of MRGs and ARGs in the strain. Overall, this study delineates environmentally beneficial traits that likely facilitates survival of Arthrobacter sp. H-02-3 within the H-02 wetland soil. Finally, this study also highlights the largely ignored public health risk associated with the co-development of ARGs and MRGs in bacteria native to historically contaminated soils.201932010097
609910.9995Culture-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
371120.9995Characterization 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
610930.9995Studies 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
610740.9995Metagenomic and genomic analysis of heavy metal-tolerant and -resistant bacteria in resource islands in a semi-arid zone of the Colombian Caribbean. Bacteria from resource islands can adapt to different extreme conditions in semi-arid regions. We aimed to determine the potential resistance and tolerance to heavy metals from the bacterial community under the canopy of three resource islands in a semi-arid zone of the Colombian Caribbean. Total DNA was extracted from soil and through a metagenomics approach, we identified genes related to heavy metal tolerance and resistance under the influence of drought and humidity conditions, as well as the presence or absence of vegetation. We characterized the genomes of bacterial isolates cultivated in the presence of four heavy metals. The abundances of genes related to heavy metal resistance and tolerance were favored by soil moisture and the presence of vegetation. We observed a high abundance of resistance genes (60.4%) for Cu, Zn, and Ni, while 39.6% represented tolerance. These genes positively correlated with clay and silt content, and negatively correlated with sand content. Resistance and tolerance were associated with detoxification mechanisms involving oxidoreductase enzymes, metalloproteases, and hydrolases, as well as transmembrane proteins involved in metal transport such as efflux pumps and ion transmembrane transporters. The Bacillus velezensis C3-3 and Cytobacillus gottheilii T106 isolates showed resistance to 5 mM of Cd, Co, Mn, and Ni through detoxification genes associated with ABC pumps, metal transport proteins, ion antiporter proteins, and import systems, among others. Overall, these findings highlight the potential of bacteria from resource islands in bioremediation processes of soils contaminated with heavy metals.202438127234
611250.9995Analysis of heavy metal tolerance and genomics in an indigenous Kurthia strain from Kulik River reveals multi-metal resistance and dominance of selection pressure on codon usage patterns. Heavy metal(loid) contamination poses significant risks to biological entities and the ecosystem. Many metal(loid)-resistant bacteria have been isolated from different environmental sites, but still no work has described multi-metal resistant Kurthia sp. In this study, an indigenous Kurthia strain isolated from the surface water of River Kulik was studied to determine its level of tolerance to various metal(loid)s. This study aimed to isolate, characterize and determine the growth kinetics and efficiency of Kurthia gibsonii strain M6 to remove and bioaccumulate As(V), Ni and Pb in vitro. This study also aimed to sequence the whole genome of the bacterium, identify metal resistance genes and analyze the codon usage patterns and factors that affect the codon usage bias of these genes. The bacterium showed elevated resistance to As(V), Pb, Ni and Zn. Under metal(loid) stressed conditions, live cells of Kurthia strain M6 bioaccumulated 212.74, 91.51 and 40.38 mg g(-1) of As(V), Pb and Ni, respectively. The removal efficiency was 97%, 69.15% and 25.88% for Pb, Ni and As(V), respectively. Genome analysis revealed the existence of different genes conferring heavy metal resistance. A comprehensive analysis of codon usage patterns for metal resistance genes depicted the predominance of selection pressure as a prime force influencing codon usage patterns. This is the first time a multi-metal resistant K. gibsonii strain has been systematically studied regarding its heavy metal resistance biology. These findings will provide insights into the metal resistance mechanisms of the genus Kurthia and assist in devising new strategies for the bioremediation of metal-polluted environments.202539945867
477360.9995Draft genome analysis for Enterobacter kobei, a promising lead bioremediation bacterium. Lead pollution of the environment poses a major global threat to the ecosystem. Bacterial bioremediation offers a promising alternative to traditional methods for removing these pollutants, that are often hindered by various limitations. Our research focused on isolating lead-resistant bacteria from industrial wastewater generated by heavily lead-containing industries. Eight lead-resistant strains were successfully isolated, and subsequently identified through molecular analysis. Among these, Enterobacter kobei FACU6 emerged as a particularly promising candidate, demonstrating an efficient lead removal rate of 83.4% and a remarkable lead absorption capacity of 571.9 mg/g dry weight. Furthermore, E. kobei FACU6 displayed a remarkable a maximum tolerance concentration (MTC) for lead reaching 3,000 mg/L. To further investigate the morphological changes in E. kobei FACU6 in response to lead exposure, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed. These analyses revealed significant lead adsorption and intracellular accumulation in treated bacteria in contrast to the control bacterium. Whole-genome sequencing was performed to gain deeper insights into E. kobei's lead resistance mechanisms. Structural annotation revealed a genome size of 4,856,454 bp, with a G + C content of 55.06%. The genome encodes 4,655 coding sequences (CDS), 75 tRNA genes, and 4 rRNA genes. Notably, genes associated with heavy metal resistance and their corresponding regulatory elements were identified within the genome. Furthermore, the expression levels of four specific heavy metal resistance genes were evaluated. Our findings revealed a statistically significant upregulation in gene expression under specific environmental conditions, including pH 7, temperature of 30°C, and high concentrations of heavy metals. The outstanding potential of E. kobei FACU6 as a source of diverse genes related to heavy metal resistance and plant growth promotion makes it a valuable candidate for developing safe and effective strategies for heavy metal disposal.202338260751
610670.9995Genomic evidence reveals the extreme diversity and wide distribution of the arsenic-related genes in Burkholderiales. So far, numerous genes have been found to associate with various strategies to resist and transform the toxic metalloid arsenic (here, we denote these genes as "arsenic-related genes"). However, our knowledge of the distribution, redundancies and organization of these genes in bacteria is still limited. In this study, we analyzed the 188 Burkholderiales genomes and found that 95% genomes harbored arsenic-related genes, with an average of 6.6 genes per genome. The results indicated: a) compared to a low frequency of distribution for aio (arsenite oxidase) (12 strains), arr (arsenate respiratory reductase) (1 strain) and arsM (arsenite methytransferase)-like genes (4 strains), the ars (arsenic resistance system)-like genes were identified in 174 strains including 1,051 genes; b) 2/3 ars-like genes were clustered as ars operon and displayed a high diversity of gene organizations (68 forms) which may suggest the rapid movement and evolution for ars-like genes in bacterial genomes; c) the arsenite efflux system was dominant with ACR3 form rather than ArsB in Burkholderiales; d) only a few numbers of arsM and arrAB are found indicating neither As III biomethylation nor AsV respiration is the primary mechanism in Burkholderiales members; (e) the aio-like gene is mostly flanked with ars-like genes and phosphate transport system, implying the close functional relatedness between arsenic and phosphorus metabolisms. On average, the number of arsenic-related genes per genome of strains isolated from arsenic-rich environments is more than four times higher than the strains from other environments. Compared with human, plant and animal pathogens, the environmental strains possess a larger average number of arsenic-related genes, which indicates that habitat is likely a key driver for bacterial arsenic resistance.201424632831
771480.9995Functional traits and health implications of the global household drinking-water microbiome retrieved using an integrative genome-centric approach. The biological safety of drinking water plays a crucial role in public health protection. However, research on the drinking water microbiome remains in its infancy, especially little is known about the potentially pathogenic bacteria in and functional characteristics of the microbiome in household tap water that people are directly exposed to. In this study, we used a genomic-centric approach to construct a genetic catalogue of the drinking water microbiome by analysing 116 metagenomic datasets of household tap water worldwide, spanning nine countries/regions on five continents. We reconstructed 859 high-quality metagenome-assembled genomes (MAGs) spanning 27 bacterial and 2 archaeal phyla, and found that the core MAGs belonging to the phylum Proteobacteria encoded the highest metabolic functional diversity of the 33 key complete metabolic modules. In particular, we found that two core MAGs of Brevibacillus and Methylomona encoded genes for methane metabolism, which may support the growth of heterotrophic organisms observed in the oligotrophic ecosystem. Four MAGs of complete ammonia oxidation (comammox) Nitrospira were identified and functional metabolic analysis suggested these may enable mixotrophic growth and encode genes for reactive oxygen stress defence and arsenite reduction that could aid survival in the environment of oligotrophic drinking water systems. Four MAGs were annotated as potentially pathogenic bacteria (PPB) and thus represented a possible public health concern. They belonged to the genera Acinetobacter (n = 3) and Mycobacterium (n = 1), with a total relative abundance of 1.06 % in all samples. The genomes of PPB A. junii and A. ursingii were discovered to contain antibiotic resistance genes and mobile genetic elements that could contribute to antimicrobial dissemination in drinking water. Further network analysis suggested that symbiotic microbes which support the growth of pathogenic bacteria can be targets for future surveillance and removal.202438183799
674290.9995Influence of epiphytic bacteria on arsenic metabolism in Hydrilla verticillata. Microbial assemblages such as biofilms around aquatic plants play a major role in arsenic (As) cycling, which has often been overlooked in previous studies. In this study, arsenite (As(III))-oxidizing, arsenate (As(V))-reducing and As(III)-methylating bacteria were found to coexist in the phyllosphere of Hydrilla verticillata, and their relative activities were shown to determine As speciation, accumulation and efflux. When exposed to As(III), As(III) oxidation was not observed in treatment H(III)-B, whereas treatment H(III)+B showed a significant As(III) oxidation ability, thereby indicating that epiphytic bacteria displayed a substantial As(III) oxidation ability. When exposed to As(V), the medium only contained 5.89% As(III) after 48 h of treatment H(V)-B, while an As(III) content of 86.72% was observed after treatment H(V)+B, thereby indicating that the elevated As(III) in the medium probably originated from As(V) reduction by epiphytic bacteria. Our data also indicated that oxidizing bacteria decreased the As accumulation (by approximately 64.44% compared with that of treatment H(III)-B) in plants, while reducing bacteria played a critical role in increasing As accumulation (by approximately 3.31-fold compared with that of treatment H(V)-B) in plants. Regardless of whether As(III) or As(V) was supplied, As(III) was dominant in the plant tissue (over 75%). Furthermore, the presence of epiphytic bacteria enhanced As efflux by approximately 9-fold. Metagenomic analysis revealed highly diverse As metabolism genes in epiphytic bacterial community, particularly those related to energetic metabolism (aioAB), and As resistance (arsABCR, acr3, arsM). Phylogenetic analysis of As metabolism genes revealed evidence of both vertical inheritance and horizontal gene transfer, which might have contributed to the evolution of the As metabolism genes. Taken together, our research suggested that the diversity of As metabolism genes in epiphytic bacterial community is associated with aquatic submerged macrophytes which may play an important role in As biogeochemistry in aquatic environments.202032114122
3860100.9995Mobility 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
6103110.9995Culture-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
3712120.9995Enumeration 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
3233130.9995A Metagenomic Investigation of Potential Health Risks and Element Cycling Functions of Bacteria and Viruses in Wastewater Treatment Plants. The concentration of viruses in sewage sludge is significantly higher (10-1000-fold) than that found in natural environments, posing a potential risk for human and animal health. However, the composition of these viruses and their role in the transfer of pathogenic factors, as well as their role in the carbon, nitrogen, and phosphorus cycles remain poorly understood. In this study, we employed a shotgun metagenomic approach to investigate the pathogenic bacteria and viral composition and function in two wastewater treatment plants located on a campus. Our analysis revealed the presence of 1334 amplicon sequence variants (ASVs) across six sludge samples, with 242 ASVs (41.22% of total reads) identified as pathogenic bacteria. Arcobacter was found to be the most dominant pathogen accounting for 6.79% of total reads. The virome analysis identified 613 viral genera with Aorunvirus being the most abundant genus at 41.85%. Approximately 0.66% of these viruses were associated with human and animal diseases. More than 60% of the virome consisted of lytic phages. Host prediction analysis revealed that the phages primarily infected Lactobacillus (37.11%), Streptococcus (21.11%), and Staphylococcus (7.11%). Furthermore, our investigation revealed an abundance of auxiliary metabolic genes (AMGs) involved in carbon, nitrogen, and phosphorus cycling within the virome. We also detected a total of 113 antibiotic resistance genes (ARGs), covering major classes of antibiotics across all samples analyzed. Additionally, our findings indicated the presence of virulence factors including the clpP gene accounting for approximately 4.78%, along with toxin genes such as the RecT gene representing approximately 73.48% of all detected virulence factors and toxin genes among all samples analyzed. This study expands our understanding regarding both pathogenic bacteria and viruses present within sewage sludge while providing valuable insights into their ecological functions.202438675877
6104140.9995The 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
6108150.9995Genes involved in arsenic transformation and resistance associated with different levels of arsenic-contaminated soils. BACKGROUND: Arsenic is known as a toxic metalloid, which primarily exists in inorganic form [As(III) and As(V)] and can be transformed by microbial redox processes in the natural environment. As(III) is much more toxic and mobile than As(V), hence microbial arsenic redox transformation has a major impact on arsenic toxicity and mobility which can greatly influence the human health. Our main purpose was to investigate the distribution and diversity of microbial arsenite-resistant species in three different arsenic-contaminated soils, and further study the As(III) resistance levels and related functional genes of these species. RESULTS: A total of 58 arsenite-resistant bacteria were identified from soils with three different arsenic-contaminated levels. Highly arsenite-resistant bacteria (MIC > 20 mM) were only isolated from the highly arsenic-contaminated site and belonged to Acinetobacter, Agrobacterium, Arthrobacter, Comamonas, Rhodococcus, Stenotrophomonas and Pseudomonas. Five arsenite-oxidizing bacteria that belonged to Achromobacter, Agrobacterium and Pseudomonas were identified and displayed a higher average arsenite resistance level than the non-arsenite oxidizers. 5 aoxB genes encoding arsenite oxidase and 51 arsenite transporter genes [18 arsB, 12 ACR3(1) and 21 ACR3(2)] were successfully amplified from these strains using PCR with degenerate primers. The aoxB genes were specific for the arsenite-oxidizing bacteria. Strains containing both an arsenite oxidase gene (aoxB) and an arsenite transporter gene (ACR3 or arsB) displayed a higher average arsenite resistance level than those possessing an arsenite transporter gene only. Horizontal transfer of ACR3(2) and arsB appeared to have occurred in strains that were primarily isolated from the highly arsenic-contaminated soil. CONCLUSION: Soils with long-term arsenic contamination may result in the evolution of highly diverse arsenite-resistant bacteria and such diversity was probably caused in part by horizontal gene transfer events. Bacteria capable of both arsenite oxidation and arsenite efflux mechanisms had an elevated arsenite resistance level.200919128515
6102160.9994Isolation of highly copper-resistant bacteria from deep-sea hydrothermal fields and description of a novel species Marinobacter metalliresistant sp. nov. INTRODUCTION: Hydrothermal vents, rich in heavy metals, provided a unique niche for heavy metal resistant microbes. However, knowledge about copper resistant microbes in deep sea hydrothermal vents is still limited. METHODS: The copper-resistant bacteria were isolated from deep-sea hydrothermal vent samples and conducted thorough physical, phylogenetic, and genomic analyses to elucidate their copper resistance capability and related genes. RESULTS: Twelve highly copper-resistant bacteria (up to 6-10 mM) were isolated from deep sea hydrothermal fields They were affiliated with the Pseudoalteromonas (4), Marinobacter (3), Halomonas (2), Psychrobacter (1), and Pseudomonas (1) genus in the α-Proteobacteria, and the Sphingomonas (1) genus in the β-Proteobacteria. The presence of copper in the medium obviously induced the amount of polysaccharides and proteins in the crude extracellular polymeric substances (EPS) produced by Halomonas sp. CuT 3-1, Pseudoalteromonas sp. CuT 4-3 and Marinobacter metalliresistant CuT 6, which could absorb 40 to 50 mg•g(-1) copper. We further described a novel species, Marinobacter metalliresistant sp. nov. CuT 6(T), which exhibited a higher copper resistance and encoded more heavy metal resistance-related genes than other Marinobacter species. DISCUSSION: It revealed that the copper resistance capability exhibited by these strains in hydrothermal fields is likely attributed to the production of exopolymeric substances, such as polysaccharides and proteins, as well as active transport or efflux mechanisms for heavy metals.202439234539
7965170.9994Screening 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
3853180.9994Co-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
6893190.9994Heavy metal and antibiotic resistance in four Indian and UK rivers with different levels and types of water pollution. Heavy metal pollution can enhance the level of antibiotic resistance, posing concerns to ecosystem and public health. Here, we investigated heavy metal concentrations, heavy metal resistant bacteria and antibiotic resistant bacteria and their corresponding resistant genes, and integrons in four different river environments, i.e., low heavy metals and low wastewater, high heavy metals and low wastewater, low heavy metals and high wastewater, and high heavy metals and high wastewater levels. Heavy metals were found to show positive and significant correlations with heavy metal resistance and antibiotic resistance and integrons (r > 0.60, p < 0.05), indicating that heavy metal selective pressure can cause heavy metal and antibiotic resistance to be transmitted simultaneously via integrons, which can result in the development of multi-resistant bacteria in the heavy metal-polluted environments. Moreover, there were significant associations between heavy metal resistance and antibiotic resistance (r > 0.60, p < 0.05), demonstrating heavy metal and antibiotic resistance are connected via a same or related mechanism. Class 1 integrons were found to have strong correlations with heavy metals and heavy metal resistance and antibiotic resistance (r > 0.60, p < 0.05), indicating a higher occurrence of antibiotic resistance co-selection in the heavy metal-polluted environments.202336174689