title: Identification of genes conferring arsenic resistance to Escherichia coli from an effluent treatment plant sludge metagenomic library.
abstract: The majority of bacteria elude culture in the laboratory. A metagenomic approach provides culture-independent access to the gene pool of the whole bacterial community. A metagenomic library was constructed from an industrial effluent treatment plant sludge containing about 1.25 Gb of microbial community DNA. Two arsenic-resistant clones were selected from the metagenomic library. Clones MT3 and MT6 had eight- and 18-fold higher resistance to sodium arsenate in comparison with the parent strain, respectively. The clones also showed increased resistance to arsenite but not to antimony. Sequence analysis of the clones revealed genes encoding for putative arsenate reductases and arsenite efflux pumps. A novel arsenate resistance gene (arsN) encoding a protein with similarity to acetyltransferases was identified from clone MT6. ArsN homologues were found to be closely associated with arsenic resistance genes in many bacterial genomes. ArsN homologues were found fused to putative arsenate reductases in Methylibium petroleiphilum PM1 and Anaeromyxobacter dehalogenans 2CP-C and with a putative arsenite chaperone in Burkholderia vietnamiensis G4. ArsN alone resulted in an approximately sixfold higher resistance to sodium arsenate in wild-type Escherichia coli W3110.
authors.affiliation: Microbial Genomics and Biotechnology Group, Institute of Genomics and Integrative Biology, Council of Scientific and Industrial Research (CSIR), Delhi, India.
authors.forename: Nar Singh
authors.initials: NS
authors.lastname: Chauhan
authors.forename: Ravi
authors.initials: R
authors.lastname: Ranjan
authors.forename: Hemant J
authors.initials: HJ
authors.lastname: Purohit
authors.forename: Vipin C
authors.initials: VC
authors.lastname: Kalia
authors.forename: Rakesh
authors.initials: R
authors.lastname: Sharma
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D001149:Arsenates / Q000494:pharmacology; D001151:Arsenic / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D015698:Genomic Library; D007220:Industrial Waste; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D001149:Arsenates; D029968:Escherichia coli Proteins; D007220:Industrial Waste; D012722:Sewage; D000123:Acetyltransferases; D001151:Arsenic; C025657:arsenic acid