Desulfocarbo indianensis gen. nov., sp nov., a benzoate-oxidizing, sulfate-reducing bacterium isolated from water extracted from a coal bed

A novel, strictly anaerobic, sulfate-reducing bacterium, designated strain SCBMT, was isolated from water extracted from a coal bed in Indiana, USA. The isolate was characterized by a polyphasic taxonomic approach that included phenotypic and genotypic characterizations. Cells of strain SCBMT were vibrio-shaped, polarly flagellated, Gram-negative, motile, oxidase-negative and weakly catalase-positive. Growth of strain SCBMT was observed at NaCl concentrations ranging from 0 to 300 mM. However, no growth was observed when 1 M or more NaCl was present. Growth was observed at 16-37 degrees C, with optimal growth at 30 degrees C. The optimum pH for growth was 7, although growth was observed from pH 6.5 to 8. The doubling time under optimal growth conditions (30 degrees C, pH 7, 2.5 mM benzoate, 14 mM sulfate) was 2.7 days. Bicarbonate, HEPES, PIPES and MES were effective buffers for growth of strain SCBMT, but citrate inhibited growth. When sulfate was provided as the electron acceptor, strain SCBMT grew autotrophically with hydrogen as the electron donor and heterotrophically on benzoate, formate, acetate, pyruvate, butyrate, fumarate, succinate and palmitate. None of the substrates tested supported fermentative growth. Thiosulfate and sulfate were used as electron acceptors coupled to benzoate oxidation, but sulfite, elemental sulfur, DMSO, anthraquinone 2,6-disulfonate, nitrate, nitrite, ferric citrate, hydrous iron oxide and oxygen were not. The G+C content of genomic DNA was 62.5 mol%. The major cellular fatty acids were anteiso-C-15:0 and C-18:1 omega 7c. Phylogenetic analysis based on 16S rRNA gene sequencing placed strain SCBMT into a distinct lineage within the class Deltaproteobacteria. The closest, cultivated phylogenetic relative of strain SCBMT was Desulfarculus baarsii DSM 2075(T), with only 91.7% 16S rRNA gene sequence identity. On the basis of phenotypic and genotypic analyses, strain SCBMT represents a hovel genus and species of sulfate-reducing bacteria, for which the name Desulfocarbo indianensis gen. nov., sp. nov. is proposed. The type strain of Desulfocarbo indianensis is SCBMT (=DSM 28127(T)=JCM 19826(T)). Desulfocarbo is the second genus of the order Desulfarculales.