Caloramator viterbensis sp. nov., a novel thermophilic, glycerol-fermenting bacterium isolated from a hot spring in Italy.

A moderately thermophilic, anaerobic bacterium, strain JW/MS-VS5T, was isolated from a mixed sediment/water sample of a hot spring at Bagnaccio (near Viterbo, Italy). The cells of this organism were straight to slightly curved rods, 0.4-0.6 x 2.03.0 microm in dimension. Cells occurred singly and stained Gram-positive. The temperature range for growth at pH(25C) 6.0 was 33-64 degrees C, the optimum being 58 degrees C. The pH(25C) range for growth was from 5.0 to 7.8, the optimum being 6.0-6.5. The substrates utilized included glycerol, glucose, fructose, mannose, galactose, sucrose, cellobiose, lactose, starch and yeast extract. Acetate and 1,3-propanediol were the only detectable organic products of glycerol fermentation; significant amounts of H2 were produced during growth. The strain was unable to grow autotrophically in the presence of H2 and CO2. The main products of glucose fermentation were CO2, H2, acetate and ethanol. Single amino acids, including serine, glutamine, threonine, leucine, methionine, aspartate, valine and histidine (but not arginine), served as carbon sources. Growth was completely inhibited by ampicillin, chloramphenicol, erythromycin, rifampicin and kanamycin at 100 microg ml(-1) and was retarded by streptomycin and tetracycline. The G+C content of the DNA was 32 mol% (HPLC). According to 16S rDNA sequence analysis, the isolate is located within the Gram-type positive Bacillus-Clostridium branch of the phylogenetic tree. On the basis of physiological properties and phylogenetic analysis, it is proposed that strain JW/MS-VS5T (the only, and type, strain) (= DSM 13723T = ATCC PTA 584T), constitutes the new species Caloramator viterbensis.