title: Microbial oxidation of arsenite in a subarctic environment: diversity of arsenite oxidase genes and identification of a psychrotolerant arsenite oxidiser.
abstract: BACKGROUND
  Arsenic is toxic to most living cells. The two soluble inorganic forms of arsenic are arsenite (+3) and arsenate (+5), with arsenite the more toxic. Prokaryotic metabolism of arsenic has been reported in both thermal and moderate environments and has been shown to be involved in the redox cycling of arsenic. No arsenic metabolism (either dissimilatory arsenate reduction or arsenite oxidation) has ever been reported in cold environments (i.e. < 10 degrees C).
  
  
  RESULTS
  Our study site is located 512 kilometres south of the Arctic Circle in the Northwest Territories, Canada in an inactive gold mine which contains mine waste water in excess of 50 mM arsenic. Several thousand tonnes of arsenic trioxide dust are stored in underground chambers and microbial biofilms grow on the chamber walls below seepage points rich in arsenite-containing solutions. We compared the arsenite oxidisers in two subsamples (which differed in arsenite concentration) collected from one biofilm. 'Species' (sequence) richness did not differ between subsamples, but the relative importance of the three identifiable clades did. An arsenite-oxidising bacterium (designated GM1) was isolated, and was shown to oxidise arsenite in the early exponential growth phase and to grow at a broad range of temperatures (4-25 degrees C). Its arsenite oxidase was constitutively expressed and functioned over a broad temperature range.
  
  
  CONCLUSIONS
  The diversity of arsenite oxidisers does not significantly differ from two subsamples of a microbial biofilm that vary in arsenite concentrations. GM1 is the first psychrotolerant arsenite oxidiser to be isolated with the ability to grow below 10 degrees C. This ability to grow at low temperatures could be harnessed for arsenic bioremediation in moderate to cold climates.
authors.affiliation: Institute of Structural and Molecular Biology, UCL, Darwin Building, London, UK.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Osborne
authors.forename: Heather E
authors.initials: HE
authors.lastname: Jamieson
authors.forename: Karen A
authors.initials: KA
authors.lastname: Hudson-Edwards
authors.forename: D Kirk
authors.initials: DK
authors.lastname: Nordstrom
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Walker
authors.forename: Seamus A
authors.initials: SA
authors.lastname: Ward
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Santini
mesh_terms: D001110:Arctic Regions; D018053:Arsenites / Q000378:metabolism*; D001419:Bacteria / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002170:Canada; D005618:Fresh Water / Q000382:microbiology*; D008906:Mining; D008969:Molecular Sequence Data; D015873:Northwest Territories; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny
chemical_list: D018053:Arsenites; D001426:Bacterial Proteins; D010088:Oxidoreductases; C078179:arsenite oxidase; C015001:arsenite