Thiovirga sulfuroxydans gen. nov., sp. nov., a chemolithoautotrophic sulfur-oxidizing bacterium isolated from a microaerobic waste-water biofilm.

A novel mesophilic, chemolithoautotrophic, sulfur-oxidizing bacterium, designated strain SO07(T), was isolated from a microaerobic waste-water biofilm. Chemolithoautotrophic growth was observed with elemental sulfur, sulfide and thiosulfate as sole electron donors and oxygen as electron acceptor. Anaerobic and heterotrophic growth were not observed. Nitrate was not used as a terminal electron acceptor. The optimum pH and temperature for growth were pH 7.5 and 30 degrees C, respectively. The major isoprenoid quinone was Q-8. The DNA G + C content of strain SO07(T) was 47.1 mol%. Phylogenetic analysis of 16S rRNA gene sequences demonstrated that strain SO07(T) formed a monophyletic group in the gamma-Proteobacteria with only 89 % similarity to members of the genus Halothiobacillus, its nearest phylogenetic neighbours. In addition, the isolate differed from members of the genus Halothiobacillus in its requirement for and tolerance of NaCl; strain SO07(T) was unable to grow in NaCl concentrations of more than 180 mM. On the basis of phylogenetic, chemotaxonomic and physiological data, it is proposed that isolate SO07(T) (=JCM 12417(T) = ATCC BAA-1033(T)) represents the type strain of a novel species in a new genus, Thiovirga sulfuroxydans gen. nov., sp. nov.