Desulfonatronum cooperativum sp nov., a novel hydrogenotrophic, alkaliphilic, sulfate-reducing bacterium, from a syntrophic culture growing on acetate

A novel alkaliphilic, sulfate-reducing bacterium was isolated from a syntrophic acetate-decomposing community enriched from samples of the soda lake Khadin, Tuva, Russia; the isolate was designated strain Z-7999(T). Cells of strain Z-7999(T) were vibrioid, Gram-negative, 0.4-0.5 x 1.0-2.5 pm and motile by means of a polar flagellum. The temperature range for growth was 15-40 degrees C, with an optimum of 35-38 degrees C. The pH range for growth was 6.7-10.3, with an optimum of pH 8.0-9.0. The NaCl concentration range for growth was 1-80 g I-1. The novel isolate was obligately anaerobic, was alkaliphilic with a broad pH range and had an obligate requirement for carbonate ions in the growth medium. In the presence of sulfate as electron acceptor, it grew with hydrogen, formate and lactate. It was not able to ferment sugars, organic acids, amino acids or peptides. During growth on formate, strain Z-7999(T) reduced sulfite and thiosulfate to sulfide. It was able to grow lithoheterotrophically with sulfate and formate when acetate was added as a carbon source for biosynthesis of biomass. The G + C content of the genomic DNA of strain Z-7999(T) was 56.5 mol%. Results of comparative 16S rRNA gene sequence analyses revealed that strain Z-7999(T) was part of the delta-Proteobacteria and clustered with other members of the genus Desulfonatronum (similarity values of 95-2 and 95.3% to Desulfonatronum lacustre and Desulfonatronum thiodismutans, respectively). DNA-DNA hybridization with D. lacustre was 37%. On the basis of physiological and phylogenetic data, it is proposed that strain Z-7999(T) (=DSM 16749(T) =VKM B-2329(T)) should be placed in the genus Desulfonatronum as a representative of a novel species, Desulfonatronum cooperativum sp. nov.