Defluviitoga tunisiensis gen. nov., sp. nov., a thermophilic bacterium isolated from a mesothermic and anaerobic whey digester

<jats:p>Strain SulfLac1<jats:sup>T</jats:sup>, a thermophilic, anaerobic and slightly halophilic, rod-shaped bacterium with a sheath-like outer structure (toga), was isolated from a whey digester in Tunisia. The strain’s non-motile cells measured 3–30×1 µm and appeared singly, in pairs or as long chains. The novel strain reduced thiosulfate and elemental sulfur, but not sulfate or sulfite, into sulfide. It grew at 37–65 °C (optimum 55 °C), at pH 6.5–7.9 (optimum pH 6.9) and with 0.2–3 % (w/v) NaCl (optimum 0.5 %). The G+C content of the strain’s genomic DNA was 33.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SulfLac1<jats:sup>T</jats:sup> was most closely related to <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="species" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.483" xlink:type="simple"> <jats:italic>Petrotoga mobilis</jats:italic> </jats:ext-link> </jats:named-content> (91.4 % sequence similarity). Based on phenotypic, phylogenetic and chemotaxonomic evidence, strain SulfLac1<jats:sup>T</jats:sup> represents a novel species of a new genus within the order <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="order" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.457" xlink:type="simple"> <jats:italic>Thermotogales</jats:italic> </jats:ext-link> </jats:named-content>, for which the name <jats:italic>Defluviitoga tunisiensis</jats:italic> gen. nov., sp. nov. is proposed. The type strain of the type species is SulfLac1<jats:sup>T</jats:sup> ( = DSM 23805<jats:sup>T</jats:sup>  = JCM 17210<jats:sup>T</jats:sup>).</jats:p>