TAXONOMIC DISTINCTION OF SACCHAROLYTIC THERMOPHILIC ANAEROBES - DESCRIPTION OF THERMOANAEROBACTERIUM-XYLANOLYTICUM GEN-NOV, SP-NOV, AND THERMOANAEROBACTERIUM-SACCHAROLYTICUM GEN-NOV, SP-NOV - RECLASSIFICATION OF THERMOANAEROBIUM-BROCKII, CLOSTRIDIUM-THERMOSULFUROGENES, AND CLOSTRIDIUM-THERMOHYDROSULFURICUM E100-69 AS THERMOANAEROBACTER-BROCKII COMB-NOV, THERMOANAEROBACTERIUM-THERMOSULFURIGENES COMB-NOV, AND THERMOANAEROBACTER-THERMOHYDROSULFURICUS COMB-NOV, RESPECTIVELY - AND TRANSFER OF CLOSTRIDIUM-THERMOHYDROSULFURICUM 39E TO THERMOANAEROBACTER-ETHANOLICUS

Two thermophilic, anaerobic, xylan-degrading bacteria, strains B6A-RI(T) (T = type strain) and LX-11T, were isolated from Frying Pan Springs in Yellowstone National Park. These organisms grew chemoorganotrophically by utilizing xylan and starch but not cellulose, as well as a number of di- and monosaccharides, including glucose and xylose. Both organisms had the same optimum temperature and pH for growth (60-degrees-C and pH 6.0). The fermentation products included acetate, ethanol, lactate, CO2, and H-2. Both organisms were rod shaped and deposited sulfur on their cells. The major difference between the two isolates was in spore formation; strain LX-11T sporulated, whereas strain B6A-RI(T) did not. Strains LX-11T and B6A-RI(T) were compared with other thermophilic, anaerobic, xylan-degrading bacteria by performing DNA-DNA hybridizations and total protein analyses in order to determine the relationships of these organisms. Three different groups were identified, and new taxonomic assignments are proposed. Clostridium thermocellum LQRI was least closely related to the other seven strains studied and is placed in group I, retaining its original taxonomic assignment. Clostridium thermosulfurogenes 4B(T) and new isolates B6A-RI(T) and LX-11T are closely related and fall into group II, for which the new genus Thermoanaerobacterium is proposed. Isolate LX-11T is designated Thermoanaerobacterium xylanolyticum sp. nov., and isolate B6A-RI(T) is designated Thermoanaerobacterium saccharolyticum sp. nov. Thermoanaerobacterium thermosulfurigenes 4B(T) (originally C. thermosulfurogenes) is the type strain of the type species of the genus. Group III strains are placed in the genus Thermoanaerobacter; this group includes Thermoanaerobacter ethanolicus JW200T, Clostridium thermohydrosulfuricum 39E and E100-69T, and Thermoanaerobium brockii HTD4T. Thermoanaerobium brockii HTD4T is renamed Thermoanaerobacter brockii comb. nov., and C. thermohydrosulfuricum E100-69T is renamed Thermoanaerobacter thermohydrosulfuricus comb. nov. C. thermohydrosulfuricum 39E is nearly identical to Thermoanaerobacter ethanolicus JW200T, and these organisms are considered members of the same species. Therefore, C. thermohydrosulfuricum 39E is renamed Thermoanaerobacter ethanolicus 39E; strain JW200 is the type strain of Thermoanaerobacter ethanolicus.