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

A thermophilic, anaerobic, spore-forming, dissimilatory Fe(III)-reducing ba cterium, designated strain SR4(T), was isolated from sediment of newly form ed hydrothermal vents in the area of the eruption of Karymsky volcano on th e Kamchatka peninsula. Cells of strain SR4(T) were straight-to-curved, peri trichous rods, 0.4-0.6 mu m in diameter and 3.5-9.0 mu m in length, and exh ibited a slight tumbling motility. Strain SR4(T) 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. T he ph range for growth was 4.8-8.2, with an optimum at 6.3-6.5. Strain SR4( T) grew anaerobically with peptone as carbon source. Amorphous iron(III) ox ide present in the medium stimulated the growth of strain SR4(T); cell numb ers increased with the concomitant accumulation of Fe(II). In the presence of Fe(III), strain SR4(T) grew on H-2/CO2 and utilized molecular hydrogen. Strain SR4(T) reduced 9,10-anthraquinone-2,6-disulfonic acid, sulfite, thio sulfate, elemental sulfur and MnO2. Strain SR4(T) did not reduce nitrate or sulfate and was not capable of growth with O-2. The fermentation products from glucose were ethanol, lactate, H-2 and CO2. The G+C content of DNA was 32 mol%. 16S rDNA sequence analysis placed the organism in the genus Therm oanaerobacter. On the basis of physiological properties and phylogenetic an alysis, it is proposed that strain SR4(T) (= DSM 12299(T)) should be assign ed to a new species, Thermoanaerobacter siderophilus sp. nov.