Chromosomal co-existence of metal and antibiotic resistance genes in bacteria offers a new perspective to the bacterial resistance proliferation in contaminated environment. In this study, an arsenotrophic bacteriumAchromobacter xylosoxidansBHW-15, isolated from Arsenic (As) contaminated tubewell water in the Bogra district of Bangladesh, was analyzed using high throughput Ion Torrent Personal Genome Machine (PGM) complete genome sequencing scheme to reveal its adaptive potentiality. The assembled draft genome ofA. xylosoxidansBHW-15 was 6.3 Mbp containing 5,782 functional genes, 1,845 pseudo genes, and three incomplete phage signature regions. Comparative genome study suggested the bacterium to be a novel strain ofA. xylosoxidansshowing significant dissimilarity with other relevant strains in metal resistance gene islands. A total of 35 metal resistance genes along with arsenite-oxidizingaioSXBA, arsenate reducingarsRCDAB, and mercury resistancemerRTPADEoperonic gene cluster and 20 broad range antibiotic resistance genes including β-lactams, aminoglycosides, and multiple multidrug resistance (MDR) efflux gene complex with a tripartite system OM-IM-MFP were found co-existed within the genome. Genomic synteny analysis with reported arsenotrophic bacteria revealed the characteristic genetic organization ofarsandmeroperonic genes, rarely described in β-Proteobacteria. A transposonTn21and mobile element protein genes were also detected to the end ofmer(mercury) operonic genes, possibly a carrier for the gene transposition. In vitro antibiotic susceptibility assay showed a broad range of resistance against antibiotics belonging to β-lactams, aminoglycosides, cephalosporins (1st, 2nd, and 3rd generations), monobactams and even macrolides, some of the resistome determinants were predicted during in silico analysis. KEGG functional orthology analysis revealed the potential of the bacterium to utilize multiple carbon sources including one carbon pool by folate, innate defense mechanism against multiple stress conditions, motility, a proper developed cell signaling and processing unit and secondary metabolism-combination of all exhibiting a robust feature of the cell in multiple stressed conditions. The complete genome of the strain BHW-15 stands as a genetic basis for the evolutionary adaptation of metal and the antibiotic coexistence phenomenon in an aquatic environment.

Metagenomic analysis provides in-depth understanding of microbe mediated Arsenic (As) metabolism. The present study aims atmetagenomic analysis of the distribution, diversity, and abundance of bacteriome in arsenic affected groundwater and surrounding soils collected fromBogra district of Bangladesh. Metagenomic DNA was extracted from two groundwater samples BCW3 andBCW4 (As content10μgL-1 and 500 μgL-1, respectively), and two tube-well surrounding soil samples BSS1 and BCS5 (As content335 μgkg-1 and 492 μgkg-1),where As rich water flows off. Metagenomic analysis of six hypervariable regions of 16S rRNA gene resulted in a total of 788709 processed sequence reads and 5878 operational taxonomic units (OTUs). Bacterial richness, abundance and diversity (alpha and beta) were higher in BCW4 (85 genera) than BCW3 (19 genera) whereas both soil samples exhibited almost similar richness and diversity. Predominant genera in BCW3 were Pseudomonas, Microbacterium, Achromobacterwhereas Acinetobacter, Thiothrix, Stenotrophomonas, Paracoccus, Dechloromonas dominated in BCW4. Soils were co-dominated with more than hundreds of genera with a high relative abundance of Bacillus, Rhodoplanesand Pseudomonas.Metagenomic investigation explored potentialarsenotrophicbacteriome. Exploring microbial community might help to understand the biogeochemistry of As affected groundwater and surrounding soil environment. Bangladesh J Microbiol, Volume 39, Number 1, June 2022, pp 31-38