Isolation and characterization of a novel As(V)-reducing bacterium: Implications for arsenic mobilization and the genus Desulfitobacterium

Dissimilatory arsenate-reducing bacteria have been implicated in the mobili zation of arsenic from arsenic-enriched sediments. An As(V)-reducing bacter ium, designated strain GBFII, was isolated from arsenic-contaminated sedime nts of Lake Coeur d'Alene, Idaho. Strain GBFII couples the oxidation of for mate to the reduction of As(V) when formate is supplied as the sole carbon source and electron donor. Additionally, strain GBFH is capable of reducing As(V), Fe(III), Se(VI), Mn(IV) and a variety of oxidized sulfur species. 1 6S ribosomal DNA sequence comparisons reveal that strain GBFII is closely r elated to Desulfitobacterium hafniense DCB-2(T) and Desulfitobacterium frap pieri PCP-1(T). Comparative physiology demonstrates that D. hafniense and D .frappieri, known for reductively dechlorinating chlorophenols, are also ca pable of toxic metal or metalloid respiration. DNA-DNA hybridization and co mparative physiological studies suggest that D. hafniense, D. frappieri, an d strain GBFII should be united into one species. The isolation of an Fe(II I)- and As(V) -reducing bacterium from Lake Coeur d'Alene suggests a mechan ism for arsenic mobilization in these contaminated sediments while the disc overy of metal or metalloid respiration in the genus Desulfitobacterium has implications for environments cocontaminated with arsenious and chlorophen olic compounds.