Arsenic resistance in the archaeon "Ferroplasma acidarmanus": new insights into the structure and evolution of the ars genes
- 244 Downloads
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.
KeywordsArsenic Resistance ars Ferroplasma acidarmanus Acidophile Evolution Phylogeny Genomics
Funding was provided by grants from the National Science Foundation and the United States Environmental Protection Agency.
- Alpers CN, Nordstrom DK, Thompson JM (1994) Seasonal variations of Zn/Cu ratios in acid mine water from Iron Mountain, California. In: Alpers CN, Blows DW (eds) Environmental geochemistry of sulfide oxidation. American Chemical Society, Washington, DC, pp 324–344Google Scholar
- Dagnac T, Padró A, Rubio R, Rauret G (1999) Speciation of arsenic in mussels by the coupled system liquid chromatography—UV irradiation—hydride generation—inductively coupled plasma mass spectrometry. Talanta 48:763–772Google Scholar
- Edwards, KJ, Schrenk MO, Hamers R, Banfield JF (1998) Microbial oxidation of pyrite: experiments using microorganisms from an extreme acidic environment. Am Miner 83:1444–1453Google Scholar
- Peters S (2001) The origins and geochemical behavior of arsenic in a fractured bedrock aquifer, New Hampshire. Ph.D. Dissertation, University of MichiganGoogle Scholar
- Saha JC, Dikshit AK, Bandyopadhyay M, Saha KC (1999) A review of arsenic poisoning and its effects on human health. Crit Rev Environ Sci Technol 29:281313Google Scholar
- United States Environmental Protection Agency (2001) National Primary Drinking Water Standards. EPA 816-F-01–007Google Scholar
- Wei X, Brockhoff-Schwegel CA, Creed JT (2001) A comparison of urinary arsenic speciation via direct nebulization and on-line photo-oxidation-hydride generation with IC separation and ICP-MS detection. J Anal At Spectrom 16:12–19Google Scholar