Abstract
A novel sulfate-reducing bacterium designated
OPF15T 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 C14:0 to C20:0. Alkyl chains present in acyl/ether and
diether glycerol lipids ranged from C16:0 to C18:0. Straight,
iso- and anteiso-configurations were found for all lipid
types. The presence of OPF15T 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 OPF15T representing the
type strain.