Mahella australiensis gen. nov., sp. nov., a moderately thermophilic anaerobic bacterium isolated from an Australian oil well

1 IRD, UR 101 Extrêmophiles, IFR-BAIM, Universités de Provence et de la Méditerranée, ESIL, Marseille, France 2 School of Biomolecular and Biomedical Sciences, Griffith University, Brisbane, Australia Correspondence Bernard Ollivier ollivier{at}esil.univ-mrs.fr A novel Gram-positive, anaerobic and moderately thermophilic bacterium, strain 50-1 BON T , was isolated from an Australian terrestrial oil reservoir. Cells were spore-forming straight rods, motile by peritrichous flagella. The optimum growth conditions were 50 °C, pH 7·5 and 0·1 % NaCl. Strain 50-1 BON T fermented arabinose, cellobiose, fructose, galactose, glucose, mannose, sucrose, xylose and yeast extract. Glucose was fermented mainly into lactate, formate, hydrogen and CO 2 . The major end product of pyruvate fermentation was acetate together with H 2 and CO 2 . Thiosulfate, sulfate, elemental sulfur and nitrate were not used as terminal electron acceptors. The DNA G+C content was 55·5 mol%. The closest phylogenetic relative of strain 50-1 BON T was Thermoanaerobacterium thermosulfurigenes (16S rRNA gene sequence similarity of 85·7 %). As strain 50-1 BON T was physiologically and phylogenetically different from members of the order ‘ Thermoanaerobacteriales ’, it is proposed that strain 50-1 BON T (=DSM 15567 T =CIP 107919 T ) be classified as the type strain of a novel species of a new genus, Mahella australiensis gen. nov., sp. nov. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain 50-1 BON T is AY331143 .