title: Detection, diversity and expression of aerobic bacterial arsenite oxidase genes.
abstract: The arsenic (As) drinking water crisis in south and south-east Asia has stimulated intense study of the microbial processes controlling the redox cycling of As in soil-water systems. Microbial oxidation of arsenite is a critical link in the global As cycle, and phylogenetically diverse arsenite-oxidizing microorganisms have been isolated from various aquatic and soil environments. However, despite progress characterizing the metabolism of As in various pure cultures, no functional gene approaches have been developed to determine the importance and distribution of arsenite-oxidizing genes in soil-water-sediment systems. Here we report for the first time the successful amplification of arsenite oxidase-like genes (aroA/asoA/aoxB) from a variety of soil-sediment and geothermal environments where arsenite is known to be oxidized. Prior to the current work, only 16 aroA/asoA/aoxB-like gene sequences were available in GenBank, most of these being putative assignments from homology searches of whole genomes. Although aroA/asoA/aoxB gene sequences are not highly conserved across disparate phyla, degenerate primers were used successfully to characterize over 160 diverse aroA-like sequences from 10 geographically isolated, arsenic-contaminated sites and from 13 arsenite-oxidizing organisms. The primer sets were also useful for confirming the expression of aroA-like genes in an arsenite-oxidizing organism and in geothermal environments where arsenite is oxidized to arsenate. The phylogenetic and ecological diversity of aroA-like sequences obtained from this study suggests that genes for aerobic arsenite oxidation are widely distributed in the bacterial domain, are widespread in soil-water systems containing As, and play a critical role in the biogeochemical cycling of As.
authors.affiliation: Thermal Biology Institute, Montana State University, Bozeman, MT 59717 USA. binskeep@montana.edu
authors.forename: William P
authors.initials: WP
authors.lastname: Inskeep
authors.forename: Richard E
authors.initials: RE
authors.lastname: Macur
authors.forename: Natsuko
authors.initials: N
authors.lastname: Hamamura
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Warelow
authors.forename: Seamus A
authors.initials: SA
authors.lastname: Ward
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Santini
mesh_terms: D001151:Arsenic / Q000032:analysis / Q000378:metabolism*; D018053:Arsenites / Q000378:metabolism; D001315:Australia; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D001673:Biodegradation, Environmental; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D010802:Phylogeny; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D014481:United States; D014874:Water Pollutants, Chemical / Q000378:metabolism
chemical_list: D018053:Arsenites; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D010088:Oxidoreductases; C078179:arsenite oxidase; C015001:arsenite; D001151:Arsenic