Thermodesulfobacterium geofontis sp. nov., a hyperthermophilic, sulfate-reducing bacterium isolated from Obsidian Pool, Yellowstone National Park

A novel sulfate-reducing bacterium designated OPF15^T was isolated from Obsidian Pool, Yellowstone National Park, Wyoming. The phylogeny of 16S rRNA and functional genes (dsrAB) placed the organism within the family Thermodesulfobacteriaceae. The organism displayed hyperthermophilic temperature requirements for growth with a range of 70–90 °C and an optimum of 83 °C. Optimal pH was around 6.5–7.0 and the organism required the presence of H₂ or formate as an electron donor and CO₂ as a carbon source. Electron acceptors supporting growth included sulfate, thiosulfate, and elemental sulfur. Lactate, acetate, pyruvate, benzoate, oleic acid, and ethanol did not serve as electron donors. Membrane lipid analysis revealed diacyl glycerols and acyl/ether glycerols which ranged from C_14:0 to C_20:0. Alkyl chains present in acyl/ether and diether glycerol lipids ranged from C_16:0 to C_18:0. Straight, iso- and anteiso-configurations were found for all lipid types. The presence of OPF15^T was also shown to increase cellulose consumption during co-cultivation with Caldicellulosiruptor obsidiansis, a fermentative, cellulolytic extreme thermophile isolated from the same environment. On the basis of phylogenetic, phenotypic, and structural analyses, Thermodesulfobacterium geofontis sp. nov. is proposed as a new species with OPF15^T representing the type strain.