Sulfurihydrogenibium kristjanssonii sp nov., a hydrogen- and sulfur-oxidizing thermophile isolated from a terrestrial Icelandic hot spring

Three thermophilic, aerobic, hydrogen- and sulfur-oxidizing bacteria were isolated from an Icelandic hot spring near the town of Hveragerdi and share >99% 16S rRNA gene sequence similarity. One of these isolates, designated strain 16628(T), was selected for further characterization. Strain 16628(T) is a motile rod, 1.5-2.5 mu m long and about 0.5 mu m wide. Growth occurred between 40 and 73 degrees C (optimally at 68 degrees C), at pH 5.3-7.8 (optimally at pH 6.6) and at NaCl concentrations between 0 and 0.5% (w/v). Strain 16628(T) grew with H(2), S(0) or S(2)O(3)(2-) as an electron donor with O(2) (up to 25%, v/v; optimally at 4-9%) as the sole electron acceptor. CO(2) and succinate were utilized as carbon sources but no organic compounds, including succinate, could be used as an energy source. The G + C content of the genomic DNA was determined to be 28.1 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain 16628(T) is a member of the genus Sulfurihydrogenibium, the closest cultivated relative being the recently described strain Sulfurihydrogenibium rodmanii UZ3-5(T) (98.2% sequence similarity). On the basis of the physiology and phylogeny of this organism, strain 16628(T) represents a novel species of the genus Sulfurihydrogenibium, for which the name Sulfurihydrogenibium kristjanssonii sp. nov. is proposed. The type strain is 16628(T) (= DSM 19534(T) = OCM 901(T) = ATCC BAA-1535(T)).