Caloramator boliviensis sp. nov., a novel 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, 2.5 μm long and 0.5 μm wide, approximately. The strain was variable to Gram stain, spore-forming and monotrichously flagellated. Growth of the strain was observed at 45-65 °C and at pH 5.5-8.0, at an optimum temperature of 60 °C and pH 6.5. The substrates utilized by the strain 45B(T) were xylose, cellobiose, glucose, arabinose, sucrose, lactose, maltose, fructose, galactose, mannose, glycerol, xylan, carboxy methylcellulose and yeast extract. The main fermentation product from xylose and cellobiose was ethanol (0.70 and 0.45 grams of 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). Polar lipids such as DPG, PG, PE, NGL and other 15 unidentified lipids were predominant in the cell. The DNA G+C content of strain 45B(T) was 32.6 mol %. Phylogenetic analysis based on 16S rDNA 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, 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))