Desulfonatronobacter acidivorans gen. nov., sp. nov. and Desulfobulbus alkaliphilus sp. nov., haloalkaliphilic heterotrophic sulfate-reducing bacteria from soda lakes.

Two types of heterotrophic sulfate-reducing bacteria (SRB) were isolated from anoxic sediments of hypersaline soda lakes in Kulunda Steppe (Altai, Russia). The isolates used propionate as an energy and carbon source. Strain APT2(T) was enriched and isolated with thiosulfate as the electron acceptor. Strains APS1(T) and ASS1 were isolated with sulfate. Strain APT2(T) was a short rod and motile with a single subpolar flagellum, while strains APS1(T) and ASS1 were lemon-shaped oval rods and motile with a single polar flagellum and thin flagella-like filaments. Strain APT2(T) grew by complete oxidation of C(3)-C(8) fatty acids with thiosulfate or sulfate as the electron acceptor, while strains APS1(T) and ASS1 were much less versatile and utilized only propionate and pyruvate as the electron donor and carbon source with sulfate or sulfite as the electron acceptor. Furthermore, strains APS1(T) and ASS1 oxidized propionate incompletely to form acetate. All of the isolates were moderately halophilic and obligately alkaliphilic. Phylogenetic analysis based on 16S rRNA gene sequences placed the isolates in the order Desulfobacterales of the class Deltaproteobacteria. Strain APT2(T) belonged to the family Desulfobacteraceae and clustered with a halophilic SRB, Desulfosalsimonas propionicica PropA(T). Strains APS1(T) and ASS1 were closely related to each other and clustered with the genus Desulfobulbus of the family Desulfobulbaceae. On the basis of phenotypic and phylogenetic analysis, the isolates are proposed to represent two novel taxa, Desulfonatronobacter acidivorans gen. nov., sp. nov. (type strain of the type species APT2(T) = DSM 24257(T) = UNIQEM U853(T)) and Desulfobulbus alkaliphilus sp. nov. (type strain APS1(T) = DSM 24258(T) = UNIQEM U900(T)).