Desulfurispora thermophila gen. nov., sp. nov., a thermophilic, spore-forming sulfate-reducer isolated from a sulfidogenic fluidized-bed reactor.

A thermophilic, Gram-positive, endospore-forming, sulfate-reducing bacterium was isolated from a sulfidogenic fluidized-bed reactor treating acidic metal- and sulfate-containing water. The strain, designated RA50E1(T), was rod-shaped and motile. The strain grew at 40-67 degrees C (optimum growth at 59-61 degrees C) and pH 6.4-7.9 (optimum growth at pH 7.0-7.3). The strain tolerated up to 1 % NaCl. Sulfate, sulfite, thiosulfate and elemental sulfur were used as electron acceptors, but not nitrate, nitrite or iron(III). Electron donors utilized were H(2)/CO(2) (80 : 20, v/v), alcohols, various carboxylic acids and some sugars. Fermentative growth occurred on lactate and pyruvate. The cell wall contained meso-diaminopimelic acid and the major respiratory isoprenoid quinone was menaquinone MK-7. Major whole-cell fatty acids were iso-C(15 : 0) and iso-C(17 : 0). Strain RA50E1(T) was distantly related to representatives of the genera Desulfotomaculum, Pelotomaculum, Sporotomaculum and Cryptanaerobacter. On the basis of 16S rRNA gene sequence data, the strain cannot be assigned to any known genus. Based on the phenotypic and phylogenetic features of strain RA50E1(T), it is proposed that the strain represents a novel species in a new genus, for which the name Desulfurispora thermophila gen. nov., sp. nov. is proposed. The type strain of Desulfurispora thermophila is RA50E1(T) (=DSM 16022(T)=JCM 14018(T)).