Genome sequencing of a Thermosipho activus strain Rift-s3T, novel anaerobic, extremely thermophilic, hydrolytic bacterium isolated from a deep-sea sample from Guaymas Basin, Gulf of California.. Thermosipho activus

Thermosipho activus strain Rift-s3T is a novel anaerobic, extremely thermophilic, hydrolytic bacterium inhabiting in Riftia pachyptila sheath (Guaymas Basin, Gulf of California). The cells of the novel strain are non-spore forming rods with a Gram-negative type of cell wall surrounded by a sheath-like structure (toga). The novel isolate grew at 44-75 degrees C (optimum 65 degrees C) and pH 5.5-8.0 (optimum 6.0). Mono-, oligo- and polysaccharides and proteins are used as substrates for growth of the strain. The strain was able to reduced elemental sulphur to sulphide, and ferric iron to ferrous iron with no stimulation of its growth. Phylogenetic analysis of 16S rRNA gene sequences showed the affiliation of strain Rift-s3T with the genus Thermosipho, with Thermosipho atlanticus Ob7T as the closest relative (96.5% 16S rRNA gene sequence similarity). Strain Rift-s3T shares several features with all other species of the genus Thermosipho: it is an extremely thermophilic microorganism able to grow at broad range of NaCl concentrations; it ferments carbohydrates, producing acetate, hydrogen and carbon dioxide. However, the novel isolate possessed phenotypic characteristics that differed significantly from those of other Thermosipho members. It was able to grow on xylose and a variety of biopolymers, including cellulose, xylan, pectin, chitin, xanthan gum and beta-keratin. Similar to Thermosipho globiformans, T. melanesiensis and unpublished ‘T. ferriphilus’, strain Rift-s3T was able to reduce Fe (III), however iron reduction seems to be a non-energy-generating process in this isolate. This study is aimed to give genomic and phylogenetic insights into these important metabolic features of T. activus.