Athalassotoga saccharophila gen. nov., sp. nov., isolated from an acidic terrestrial hot spring, and proposal of Mesoaciditogales ord. nov. and Mesoaciditogaceae fam. nov. in the phylum Thermotogae

Abstract

A novel moderately thermophilic, weakly acidophilic, heterotrophic, anaerobic, short-rod bacterium having an outer sheath-like structure (toga) was isolated from a low-salt acidic terrestrial hot spring in Oku-Shiobara, Tochigi, Japan. The strain, designated NAS-01^T, grew between 30 and 60 °C (optimum 55 °C), and at pH 4.5 and 7.5 (optimum pH 5.5 to 6.0) and could not grow in media with ≥ 1 % NaCl (optimum 0 % NaCl). It utilized Fe(III), thiosulfate or l-cystine as electron acceptor for growth, and yeast extract, peptone or a variety of sugars as carbon and energy sources. The major cellular fatty acid was C_{16 : 0}, and no lipoquinone was detected. Strain NAS-01^T contained phospholipids and glycolipids, but not aminolipids. The DNA G+C content was 41.1 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the strain was included in the phylum <i>Thermotogae</i>, and was closely related to <i>Mesoaciditoga lauensis</i>. The 16S rRNA gene sequence similarity between them was 90 %, and they were deeply branched off the rest of the known <i>Thermotogae</i> species. On the basis of the phylogenetic and ecophysiological properties, strain NAS-01^T represents a novel species of a new genus in the phylum <i>Thermotogae</i>, for which we propose the name <i>Athalassotoga saccharophila</i> gen. nov., sp. nov. The type strain of the type species is NAS-01^T ( = JCM 19762^T = DSM 28954^T). In addition, we propose a new order and family, <i>Mesoaciditogales</i> ord. nov. and <i>Mesoaciditogaceae</i> fam. nov., respectively, to accommodate the novel genus and the closely related genus <i>Mesoaciditoga</i>.