A thermophilic, anaerobic, iron-reducing bacterium strain JL129W03T (=KCTC 15905T=MCCC 1A14213T) was isolated from a sulfide sample collected from the Daxi hydrothermal field (60.5° E, 6.4° N, 2919 m depth) on the Carlsberg Ridge, northwest Indian Ocean. Cells grew at 55-75 °C(optimum, 70 °C), at pH 6.0-9.0 (optimum, pH 6.0-7.0) and at NaCl concentrations of 1.5-4.5 % (w/v; optimum 3.0 %). Under optimal growth conditions, the generation time was around 85 min. The isolate was an obligate chemoorganoheterotroph, utilizing complex organic compounds, carbohydrates, organic acids and one amino acid. It was anaerobic and facultatively dependent on elemental sulphur and various forms of Fe(III) as an electron acceptor: insoluble forms and soluble forms. It did not reduce sulfite, sulphate, thiosulfate or nitrate. The G+C content of its genomic DNA was 34.0 mol%. Phylogenetic 16S rRNA gene sequence analyses revealed that its closest relative was Thermosipho atlanticus DV1140T with 95.81 % 16S rRNA sequence similarity. On the basis of physiological distinctness and phylogenetic distance, the isolate is considered to represent a novel species of the genus Thermosipho, for which the name Thermosipho ferrireducens sp. nov. is proposed. The type strain is strain JL129W03T (=KCTC 15905T;=MCCC 1A14213T).
Keywords: Fe(III)-reducing; Thermosipho ferrireducens sp. nov; deep-sea hydrothermal sulfide.