Desulfovibrio butyratiphilus sp nov., a Gram-negative, butyrate-oxidizing, sulfate-reducing bacterium isolated from an anaerobic municipal sewage sludge digester

Strictly anaerobic, mesophilic, sulfate-reducing bacterial strains were isolated from two anaerobic municipal sewage sludge digesters. One representative strain (BSYT) was characterized phenotypically and phylogenetically. Cells were Gram-negative, motile by means of a single polar flagellum, non-spore-forming, curved rods. Cells had desulfoviridin and cytochrome type c. Catalase and oxidase activities were not detected. The optimum NaCl concentration for growth was 0.5% (w/v). The optimum temperature was 35 degrees C and the optimum pH was 7.1. Strain BSYT utilized butyrate, 2-methylbutyrate, valerate, pyruvate, lactate, ethanol, 1-propanol, butanol and H-2 as electron donors for sulfate reduction. This strain grew lithoautotrophically with H-2/CO2 under sulfate-reducing conditions. Most organic electron donors were incompletely oxidized to mainly acetate, whereas 2-methylbutyrate and valerate were oxidized to equivalent amounts of acetate and propionate. Strain BSYT utilized thiosulfate as an electron acceptor, and grew with pyruvate in the absence of electron acceptors. The genomic DNA G+C content of strain BSYT was 63.3 mol%. Menaquinone MK-6(H-2) was the major respiratory quinone. Major cellular fatty acids were C-14:0, C-16:0, C-16:1 omega 7 and C-18:1 omega 7. phylogenetic analyses based on 16S rRNA and dissimilatory sulfite-reductase beta-subunit gene sequences assigned strain BSYT to the genus Desulfovibrio in the family Desulfovibrionaceae within the class Deltaproteobacteria. Its closest recognized relative based on 16S rRNA gene sequences was the type strain of Desulfovibrio putealis (95.3% similarity). On the basis of significant differences in 16S rRNA gene sequences and phenotypic characteristics, the sewage sludge strains are considered to represent a single novel species of the genus Desulfovibrio, for which the name Desulfovibrio butyratiphilus sp. nov. is proposed. The type strain is BSYT (=JCM 15519(T)=DSM 21556(T)).