Thermogemmatispora aurantia sp. nov. and thermogemmatispora argillosa sp. nov., within the class ktedonobacteria, and emended description of the genus thermogemmatispora

Two thermophilic, aerobic, Gram-stain-positive Ktedonobacteria strains, A1-2^T and A3-2^T, were isolated from geothermal soil in Japan. The strains formed orange-coloured colonies on 10-fold diluted Reasoner’s 2A medium, followed by formation of branched aerial mycelium with multiple grape-like spores. Both strains hydrolysed casein, carboxymethyl cellulose, starch, chitin and xylan, but did not liquify gelatin. Strain A1-2^T utilised sucrose and gellan gum and was inhibited by inositol, while strain A3-2^T utilised only gellan gum and was not inhibited by inositol. The DNA G+C contents of strain A1-2^T and A3-2^T were 63.2 and 63.1 mol%, respectively. Chemotaxonomic data (major fatty acid, iso-C_{17: 0}; major menaquinone, MK-9(H₂); cell-wall amino acids, ornithine, serine, glycine, glutamic acid, alanine and b-alanine; polar lipids, phosphatidylinositol, phosphatidylglycerol, diphosphatidylglycerol, one unidentified lipid, one unidentified phosphoglycolipid and three unidentified glycolipids; major cell-wall sugars, mannose, arabinose and xylose) indicate that both strains belong to the genus Thermogemmatispora. 16S rRNA gene sequence analysis indicated that strain A1-2^T was most closely related to the type strains of Thermogemmatispora onikobensis (97.7% sequence similarity), and that strain A3-2^T was most closely related to the type strains of Thermogemmatispora carboxidivorans(97.2%), but DNA–DNA hybridization shows relatedness values of <67% with previously described type strains. Moreover, 16S rRNA gene sequence similarity and DNA–DNA relatedness between strain A1-2^T and strain A3-2^T were 96.0 and 33.4%, respectively, suggesting that the two strains are genetically distinct. The two strains are proposed as Thermogemmatispora aurantia sp. nov. and Thermogemmatispora argillosa sp. nov.