title: Arsenic resistance in the archaeon "Ferroplasma acidarmanus": new insights into the structure and evolution of the ars genes.
abstract: Arsenic resistance in the acidophilic iron-oxidizing archaeon " Ferroplasma acidarmanus" was investigated. F. acidarmanus is native to arsenic-rich environments, and culturing experiments confirm a high level of resistance to both arsenite and arsenate. Analyses of the complete genome revealed protein-encoding regions related to known arsenic-resistance genes. Genes encoding for ArsR (arsenite-sensitive regulator) and ArsB (arsenite-efflux pump) homologues were found located on a single operon. A gene encoding for an ArsA relative (anion-translocating ATPase) located apart from the arsRB operon was also identified. Arsenate-resistance genes encoding for proteins homologous to the arsenate reductase ArsC and the phosphate-specific transporter Pst were not found, indicating that additional unknown arsenic-resistance genes exist for arsenate tolerance. Phylogenetic analyses of ArsA-related proteins suggest separate evolutionary lines for these proteins and offer new insights into the formation of the arsA gene. The ArsB-homologous protein of F. acidarmanus had a high degree of similarity to known ArsB proteins. An evolutionary analysis of ArsB homologues across a number of species indicated a clear relationship in close agreement with 16S rRNA evolutionary lines. These results support a hypothesis of arsenic resistance developing early in the evolution of life.
authors.affiliation: Department of Geology and Geophysics, The University of Wisconsin Madison, Madison, Wisconsin, USA. thomas.gihring@pnl.gov
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gihring
authors.forename: Philip L
authors.initials: PL
authors.lastname: Bond
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Peters
authors.forename: Jillian F
authors.initials: JF
authors.lastname: Banfield
mesh_terms: D000595:Amino Acid Sequence; D001151:Arsenic / Q000494:pharmacology*; D053501:Arsenite Transporting ATPases; D001426:Bacterial Proteins; D004352:Drug Resistance, Microbial / Q000235:genetics; D019143:Evolution, Molecular; D019766:Genes, Archaeal; D016623:Ion Pumps / Q000235:genetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D019603:Thermoplasmales / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development; D015534:Trans-Activators / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D016623:Ion Pumps; D009097:Multienzyme Complexes; D015534:Trans-Activators; D053501:Arsenite Transporting ATPases; D001151:Arsenic