Sporosalibacterium tautonense sp. nov., a thermotolerant, halophilic, hydrolytic bacterium isolated from a gold mine, and emended description of the genus Sporosalibacterium

A novel strictly anaerobic, thermotolerant, moderately halophilic, organotrophic bacterium, strain MRo-4^T, was isolated from a sample of a microbial mat, developed under the flow of subsurface water in TauTona gold mine, South Africa. Cells of the novel isolate stained Gram-positive and were motile, spore-forming rods, 0.2–0.3μm in width and 5–20μm in length. Strain MRo-4^T grew at 25–50 °C, at pH 7.0–8.8 and at an NaCl concentration of 5–100 g l^–1. The isolate was able to ferment yeast extract, peptone and mono-, oligo- and polysaccharides, including cellulose and chitin. Elemental sulfur, thiosulfate, sulfate, sulfite, nitrate, nitrite, fumarate and arsenate were not reduced. The major fatty acids were iso-C_{15: 0}, iso-C_{15: 0} dimethyl acetyl and anteiso-C_{15: 0}. The G+C content of the DNA was 32.9 mol%. Phylogenetic analysis of 16S rRNA gene sequences of strain MRo-4^T and its nearest relatives showed its affiliation to the genus Sporosalibacterium. Sporosalibacterium faouarense SOL3f37^T, the only valid published representative of the genus, appeared to be its closest relative (96.8% 16S rRNA gene sequence similarity). However, strains MRo-4^T and S. faouarense SOL3f37^T differed in temperature, pH and salinity ranges for growth, requirement for yeast extract and substrate profiles. Based on the phylogenetic analysis and physiological properties of the novel isolate, we propose a novel species, Sporosalibacterium tautonense sp. nov. The type strain is MRo-4^T (=DSM 28179^T=VKM B-2948^T).