Caldicoprobacter oshimai gen. nov., sp. nov., an anaerobic, xylanolytic, extremely thermophilic bacterium isolated from sheep faeces, and proposal of Caldicoprobacteraceae fam. nov.

An obligately anaerobic, xylanolytic, extremely thermophilic bacterium, strain JW/HY-331(T), was isolated from sheep faeces collected from a farm at the University of Georgia, USA. Cells of strain JW/HY-331(T) stained Gram-positive and were catalase-negative, non-motile rods. Single terminal endospores (0.4-0.6 mum in diameter) swelled the mother cell. Growth ranges were 44-77 degrees C (optimum 70 degrees C at pH(70 degrees C) 7.2) and pH(70 degrees C) 5.9-8.6 (optimum 7.2 at 70 degrees C). Salt tolerance was 0-2.0 % (w/v) NaCl. No growth was observed at or below 42 degrees C or at or above 79 degrees C or at pH(70 degrees C) 5.7 and below or 8.9 and above. In the presence of 0.3 % yeast extract and 0.1 % tryptone, strain JW/HY-331(T) utilized xylose, glucose, galactose, cellobiose, raffinose and xylan as carbon and energy sources, but not dextran, soluble potato starch, CM-cellulose, cellulose powder, casein or Casamino acids. Fermentation products from glucose were lactate, acetate, ethanol, CO2 and H2. The G+C content of the genomic DNA was 45.4 mol% (HPLC). Major cellular fatty acids were iso-C(17 : 0), iso-C(15 : 0) and anteiso-C(17 : 0). No respiratory quinones were detected. The cell-wall structure was a single layer (Gram-type positive) of the peptidoglycan type A1gamma; the cell-wall sugars were galactose and mannose. Based on 16S rRNA gene sequence analysis, 'Catabacter hongkongensis' HKU16 (85.4 % similarity), Caloramator fervidus ATCC 43204(T) (84.2 %) and Caloranaerobacter azorensis MV1087(T) (83.4 %) were the closest relatives, but they were only distantly related to strain JW/HY-331(T). On the basis of physiological, chemotaxonomic and phylogenetic data, isolate JW/HY-331(T) (=DSM 21659(T) =ATCC BAA-1711(T)) is proposed as the type strain of Caldicoprobacter oshimai gen. nov., sp. nov., placed in Caldicoprobacteraceae fam. nov. within the order Clostridiales of the phylum Firmicutes.