Desulfacinum subterraneum sp nov., a new thermophilic sulfate-reducing bacterium isolated from a high-temperature oil field

A new thermophilic sulfate-reducing bacterium isolated from the high-temper ature White Tiger oil field (Vietnam) is described. Cells of the bacterium are oval (0.4-0.6 by 0.6-1.8 mum), nonmotile, non-spore-forming, and gram-n egative. Growth occurs at 45 to 65 degreesC (with an optimum at 60 degreesC ) at NaCl concentrations of 0 to 50 g/l. In the course of sulfate reduction . the organism can utilize lactate, pyruvate, malate, fumarate, ethanol. sa lts of fatty acids (formate, acetate, propionate, butyrate, caproate. palmi tate), yeast extract, alanine, serine, cysteine, and H-2 + CO2 (autotrophic ally). In addition to sulfate, the bacterium can use sulfite, thiosulfate, and elemental sulfur as electron acceptors. In the absence of electron acce ptors, the bacterium can ferment pyruvate and yeast extract (a yet unrecogn ized capacity of sulfate reducers) with the formation of acetate and H-2. T he G+C content of DNA is 60.8 mol %. The level of DNA-DNA hybridization of the isolate (strain 101(T)) and Desulfacinum infernum (strain B alpha G1(T) ) is as low as 34%. Analysis of the nucleotide sequence of 16S rDNA places strain 101(T) in the phylogenetic cluster of the Desulfacinum species withi n the sulfate reducer subdivision of the delta subclass of Proteobacteria. All these results allowed the bacterium studied to be described as a new sp ecies, Desulfacinum subterraneum sp. nov., with strain 101 as the type stra in.