Sporolituus thermophilus gen. nov., sp. nov., a citrate-fermenting thermophilic anaerobic bacterium from geothermal waters of the Great Artesian Basin of Australia

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A strictly anaerobic, sluggishly motile, spore-forming, thermophilic bacterium, designated strain AeG(T), was isolated from microbial mats colonizing a runoff channel formed by free-flowing thermal waters of a bore well (New Lorne Bore; registered number 17263) in the Great Artesian Basin, Australia. Cells of strain AeG(T) were curved rods (2.0-10.0x0.8-1.0 mum) and stained Gram-negative. The strain grew optimally in tryptone-yeast extract-citrate medium at 55 degrees C (range for growth between 45 and 60 degrees C) and pH 7.0 (range for growth between pH 6.5 and 8.0). Citrate and malate, but no other organic acids, carbohydrates or amino acids could be used in the presence of up to 0.1 % yeast extract. Although yeast extract and/or tryptone were required for growth on citrate, they did not support growth as sole carbon sources. Strain AeG(T) reduced thiosulfate and sulfite in the presence of 0.2 % yeast extract, but not Fe(III), Mn(IV), sulfate, elemental sulfur, nitrate or nitrite. Growth was inhibited by chloramphenicol, streptomycin, tetracycline, penicillin and ampicillin and in the presence of NaCl concentrations >1 %. The DNA G+C content was 55.4+/-1.0 mol% as determined by the thermal denaturation method. 16S rRNA gene sequence analysis indicated that strain AeG(T) was a member of the family Veillonellaceae, class 'Clostridia', phylum 'Firmicutes' and was most closely related to members of the genus Propionispora (mean 16S rRNA gene sequence similarity value to type strains was 90.8 %). Based on these results, strain AeG(T) is considered to represent a novel species in a new genus, for which the name Sporolituus thermophilus gen. nov., sp. nov. is proposed. The type strain of the type species is AeG(T) (=JCM 15556(T)=KCTC 5668(T)).