Thermoanaerobacter siderophilus sp. nov., a novel dissimilatory Fe(III)-reducing, anaerobic, thermophilic bacterium.

A thermophilic, anaerobic, spore-forming, dissimilatory Fe(III)-reducing bacterium, designated strain SR4T, was isolated from sediment of newly formed hydrothermal vents in the area of the eruption of Karymsky volcano on the Kamchatka peninsula. Cells of strain SR4T were straight-to-curved, peritrichous rods, 0.4-0.6 micron in diameter and 3.5-9.0 microns in length, and exhibited a slight tumbling motility. Strain SR4T formed round, refractile, heat-resistant endospores in terminally swollen sporangia. The temperature range for growth was 39-78 degrees C, with an optimum at 69-71 degrees C. The pH range for growth was 4.8-8.2, with an optimum at 6.3-6.5. Strain SR4T grew anaerobically with peptone as carbon source. Amorphous iron(III) oxide present in the medium stimulated the growth of strain SR4T; cell numbers increased with the concomitant accumulation of Fe(II). In the presence of Fe(III), strain SR4T grew on H2/CO2 and utilized molecular hydrogen. Strain SR4T reduced 9,10-anthraquinone-2,6-disulfonic acid, sulfite, thiosulfate, elemental sulfur and MnO2. Strain SR4T did not reduce nitrate or sulfate and was not capable of growth with O2. The fermentation products from glucose were ethanol, lactate, H2 and CO2. The G + C content of DNA was 32 mol%. 16S rDNA sequence analysis placed the organism in the genus Thermoanaerobacter. On the basis of physiological properties and phylogenetic analysis, it is proposed that strain SR4T (= DSM 12299T) should be assigned to a new species, Thermoanaerobacter siderophilus sp. nov.