Caloramator boliviensis sp. nov., a thermophilic, ethanol-producing bacterium isolated from a hot spring

A novel moderately thermophilic, anaerobic, ethanol-producing bacterial strain, 45B^T, was isolated from a mixed sediment water sample collected from a hot spring at Potosi, Bolivia. The cells were straight to slightly curved rods approximately 2.5 μm long and 0.5 mm wide. The strain was Gramstain- variable, spore-forming and monotrichously flagellated. Growth of the strain was observed at 45-65 °C and pH 5.5-8.0, with optima of 60 °C and pH 6.5. The substrates utilized by strain 45B^T were xylose, cellobiose, glucose, arabinose, sucrose, lactose, maltose, fructose, galactose,mannose, glycerol, xylan, carboxymethylcellulose and yeast extract. The main fermentation product from xylose and cellobiose was ethanol (0.70 and 0.45 g ethanol per gram of consumed sugar, respectively). Acetate, lactate, propionate, carbon dioxide and hydrogen were also produced in minor quantities. 1,3-Propanediol was produced when glycerol-containing medium was supplemented with yeast extract. The major cellular fatty acids were anteiso-C_{15: 0}, C_{16: 0}, iso-C_{16: 0}, C_{15: 1}, iso-C_{14: 0}, C_{13: 0} and C_{14: 0}. The polar lipids diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an aminoglycolipid and 15 other unidentified lipids were predominant. The DNA G+C content of strain 45B^T was 32.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequence similarity revealed that strain 45B^T is located within the Gram-type positive Bacillus-Clostridium branch of the phylogenetic tree. On the basis of morphological and physiological properties and phylogenetic analysis, strain 45B^T represents a novel species, for which the name Caloramator boliviensis sp. nov. is proposed; the type strain is 45B^T (=DSM 22065^T=CCUG 57396^T).