A novel anaerobic, thermophilic, Fe(III)-reducing, CO-utilizing bacterium, strain 1315T, was isolated from a hot spring of Geyser Valley on the Kamchatka Peninsula. Cells of the new isolate were Gram-positive, short rods. Growth was observed at 52–70 °C, with an optimum at 65 °C, and at pH 5.5–8.5, with an optimum at pH 6.5–7.2. In the presence of Fe(III) or 9,10-anthraquinone 2,6-disulfonate (AQDS), the bacterium was capable of growth with CO and yeast extract (0.2 g l−1); during growth under these conditions, strain 1315T produced H2 and CO2 and Fe(II) or AQDSH2, respectively. Strain 1315T also grew by oxidation of yeast extract, glucose, xylose or lactate under a N2 atmosphere, reducing Fe(III) or AQDS. Yeast extract (0.2 g l−1) was required for growth. Isolate 1315T grew exclusively with Fe(III) or AQDS as an electron acceptor. The generation time under optimal conditions with CO as growth substrate was 9.3 h. The G+C content of the DNA was 41.5±0.5 mol%. 16S rRNA gene sequence analysis placed the organism in the genus Carboxydothermus (97.8 % similarity with the closest relative). On the basis of physiological features and phylogenetic analysis, it is proposed that strain 1315T should be assigned to a novel species, Carboxydothermus siderophilus sp. nov., with the type strain 1315T (=VKPM 9905BT =VKM B-2474T =DSM 21278T).
Two strictly anaerobic bacterial strains, designated SW512T and W72, were isolated from a laboratory-scale H2-producing up-flow anaerobic sludge blanket (UASB) reactor. Cells were Gram-stain-negative, non-motile and 0.3–0.4×2.0–14.5 μm; they did not form spores. Both strains grew at 24–45 °C (no growth at ≤22 °C or ≥46 °C), with optimum growth at 37 °C. The pH range for growth was 4.5–9.0 (no growth at pH≤4.2 or pH≥9.3), with optimum growth at pH 6.5–7.0. Several kinds of mono-, di- and oligosaccharides supported growth. The main end products of glucose fermentation were ethanol, acetate, hydrogen and carbon dioxide (according to the equation 1 mol glucose→1.1 mol acetate+0.6 mol ethanol+2.6 mol H2+1.6 mol CO2). The DNA G+C contents of strains SW512T and W72 were 41.9±0.5 and 42.8±0.4 mol% (T m method), respectively. Phylogenetic analysis based on 16S rRNA gene sequence similarities indicated that the two strains represent a new phyletic sublineage within the family ‘Ruminococcaceae’, with <91.3 % 16S rRNA gene sequence similarity to recognized species. On the basis of the polyphasic evidence in this study, it is proposed that the two strains represent a novel species in a new genus, for which the name Hydrogenoanaerobacterium saccharovorans gen. nov., sp. nov. is proposed; the type strain of the type species is SW512T (=AS 1.5070T=JCM 14861T).