Desulfonatronum thiodismutans sp. nov., a novel alkaliphilic, sulfate-reducing bacterium capable of lithoautotrophic growth

Abstract

A novel alkaliphilic sulfate-reducing bacterium, strain MLF1T, was isolated from sediments of soda Mono Lake, California. Gram-negative vibro-shaped cells were observed, which were 0.6-0.7 × 1.2-2.7 μm in size, motile by a single polar flagellum and occurred singly, in pairs or as short spirilla. Growth was observed at 15-48 °C (optimum, 37 °C), > 1-7% NaCl, w/v (optimum, 3%) and pH 8.0-10.0 (optimum, 9.5). The novel isolate is strictly alkaliphilic, requires a high concentration of carbonate in the growth medium and is obligately anaerobic and catalase-negative. As electron donors, strain MLF1T uses hydrogen, formate and ethanol. Sulfate, sulfite and thiosulfate (but not sulfur or nitrate) can be used as electron acceptors. The novel isolate is a lithoheterotroph and a facultative lithoautotroph that is able to grow on hydrogen without an organic source of carbon. Strain MLF1T is resistant to kanamycin and gentamicin, but sensitive to chloramphenicol and tetracycline. The DNA G + C content is 63.0 mol% (HPLC). DNA-DNA hybridization with the most closely related species, Desulfonatronum lacustre Z-7951T, exhibited 51% homology. Also, the genome size (1.6 × 109 Da) and Tm value of the genomic DNA (71 ± 2°C) for strain MLF1T were significantly different from the genome size (2.1 × 109 Da) and Tm value (63 ± 2°C) for Desulfonatronum lacustre Z-7951T. On the basis of physiological and molecular properties, the isolate was considered to be a novel species of the genus Desulfonatronum, for which the name Desulfonatronum thiodismutans sp. nov. is proposed (the type strain is MLF1T=ATCC BAA-395T=DSM 14708T).