Alkaliphilus transvaalensis gen. nov., sp. nov., an extremely alkaliphilic bacterium isolated from a deep South African gold mine

A novel extreme alkaliphile was isolated from a mine water containment dam at 3.2 km below land surface in an ultra-deep gold mine near Carletonville, South Africa. The cells of this bacterium were straight to slightly curved rods, motile by flagella and formed endospores. Growth was observed over the temperature range 20-50 °C (optimum 40 °C; 45 min doubling time) and pH range 8.5-12.5 (optimum pH 10.0). The novel isolate, one of the most alkaliphilic micro-organisms yet described, was a strictly anaerobic chemoorganotroph capable of utilizing proteinaceous substrates such as yeast extract, peptone, tryptone and casein. Elemental sulfur, thiosulfate or fumarate, when included as accessory electron acceptors, improved growth. The G+C content of genomic DNA was 36.4 mol %. Phylogenetic analysis based on the 16S rDNA sequence indicated that the isolate is a member of cluster XI within the low G+C Gram-positive bacteria, but only distantly related to previously described members. On the basis of physiological and molecular properties, the isolate represents a novel species, for which the name Alkaliphilus transvaalensis gen. nov., sp. nov. is proposed (type strain SAGM1^T = JCM 10712^T = ATCC 700919^T). The mechanism of generation of the highly alkaline microbial habitat and the possible source of the alkaliphile are discussed.