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-4T, 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, 0.2-0.3 µm in width and 5-20 µm in length. Strain MRo-4T 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-C15 : 0, iso-C15 : 0 dimethyl acetyl and anteiso-C15 : 0. The G+C content of the DNA was 32.9 mol%. Phylogenetic analysis of 16S rRNA gene sequences of strain MRo-4T and its nearest relatives showed its affiliation to the genus Sporosalibacterium. Sporosalibacteriumfaouarense SOL3f37T, the only valid published representative of the genus, appeared to be its closest relative (96.8 % 16S rRNA gene sequence similarity). However, strains MRo-4T and S. faouarense SOL3f37T 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-4T (=DSM 28179T=VKM B-2948T).