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A novel sulfate-reducing bacterium, designated C1TLV30T, was isolated from wood falls at a depth of 1693 m in the Mediterranean Sea. Cells were motile vibrios (2–4×0.5 µm). Strain C1TLV30T grew at temperatures between 15 and 45 °C (optimum 30 °C) and at pH 5.4–8.6 (optimum 7.3). It required NaCl for growth (optimum at 25 g NaCl l−1) and tolerated up to 80 g NaCl l−1. Strain C1TLV30T used as energy sources: lactate, fumarate, formate, malate, pyruvate and ethanol. The end products from lactate oxidation were acetate, H2S and CO2 in the presence of sulfate as terminal electron acceptor. Besides sulfate, thiosulfate and sulfite were also used as terminal electron acceptors, but not elemental sulfur, fumarate, nitrate or nitrite. Strain C1TLV30T possessed desulfoviridin and was piezophilic, growing optimally at 10 MPa (range 0–30 MPa). The membrane lipid composition of this strain was examined to reveal an increase in fatty acid chain lengths at high hydrostatic pressures. The G+C content of the genomic DNA was 49.6 % and the genome size was estimated at 3.5±0.5 Mb. Phylogenetic analysis of the SSU rRNA gene sequence indicated that strain C1TLV30T was affiliated to the genus Desulfovibrio with Desulfovibrio profundus being its closest phylogenetic relative (similarity of 96.4 %). On the basis of SSU rRNA gene sequence comparisons and physiological characteristics, strain C1TLV30T ( = DSM 21447T = JCM 1548T) is proposed to be assigned to a novel species of the genus Desulfovibrio, Desulfovibrio piezophilus sp. nov.

A novel, thermophilic, anaerobic bacterium that is able to tolerate hydrogen was isolated from a deep-sea hydrothermal chimney collected at the Rainbow field on the Mid-Atlantic Ridge. Cells were rod-shaped and surrounded by a sheath-like outer structure (toga); they were weakly motile by means of a polar flagellum. They appeared singly, in pairs or in short chains. They grew at 35–65 °C (optimum 60 °C), pH 4·5–8·5 (optimum pH 6·0) and 10–65 g sea salts l−1 (optimum 30–40 g l−1). The isolate was organotrophic, and able to grow on various carbohydrates or complex proteinaceous substrates. Growth was not inhibited under 100 % hydrogen or in the presence of 2 % oxygen in the gas phase. The isolate reduces sulfur, although sulfur reduction is not required for growth. The fermentation products identified on glucose were acetate, ethanol, formate, hydrogen and CO2. The G+C content of the genomic DNA was 28±1 mol%. Phylogenetic analysis of the 16S rRNA gene placed the strain within the genus Marinitoga, order Thermotogales, in the bacterial domain. On the basis of the 16S rRNA gene sequence comparisons and physiological characteristics, the isolate is considered to represent a novel species, for which the name Marinitoga hydrogenitolerans sp. nov. is proposed. The type strain is AT1271T (=DSM 16785T=JCM 12826T).