Desulfotomaculum thermosubterraneum sp. nov., a thermophilic sulfate-reducer isolated from an underground mine located in a geothermally active area

Abstract

A thermophilic, Gram-positive, endospore-forming, sulfate-reducing bacterium was isolated from an underground mine in a geothermally active area in Japan. Cells of this strain, designated RL50JIIIT, were rod-shaped and motile. The temperature range for growth was 50–72 °C (optimum growth at 61–66 °C) and the pH range was 6.4–7.8 (optimum at pH 7.2–7.4). Strain RL50JIIITtolerated up to 1.5 % NaCl, but optimum growth occurred in the presence of 0–1 % NaCl. Electron acceptors utilized were sulfate, sulfite, thiosulfate and elemental sulfur. Electron donors utilized were H2in the presence of CO2, alanine, various carboxylic acids and alcohols. Fermentative growth occurred on lactate and pyruvate. The cell wall contained mesodiaminopimelic acid and the major respiratory isoprenoid quinone was menaquinone 7 (MK-7). Major whole-cell fatty acids were iso-C15 : 0, iso-C17 : 0DMA (dimethyl acetal), iso-C15 : 0DMA and iso-C17 : 0. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed 98.7 % similarity withDesulfotomaculum solfataricumDSM 14956T. However, DNA–DNA hybridization experiments withDesulfotomaculum kuznetsovii,Desulfotomaculum luciaeandD. solfataricumand the G+C content of the DNA (54.4 mol%) allowed the differentiation of strain RL50JIIITfrom the recognized species of the genusDesulfotomaculum. Strain RL50JIIITtherefore represents a novel species, for which the nameDesulfotomaculum thermosubterraneumsp. nov. is proposed. The type strain is RL50JIIIT(=DSM 16057T=JCM 13837T).