Thermogemmatispora onikobensis gen. nov., sp. nov. and Thermogemmatispora foliorum sp. nov., isolated from fallen leaves on geothermal soils, and description of Thermogemmatisporaceae fam. nov. and Thermogemmatisporales ord. nov. within the class Ktedonobacteria

Abstract

Two thermophilic, Gram-stain-positive, sporulating bacterial strains, which formed branched vegetative and aerial mycelia, were isolated from fallen leaves sampled from geothermal soils and designated ONI-1T and ONI-5T. Strain ONI-1T grew at 50–74 °C, with optimum growth at 60–65 °C, and strain ONI-5T grew at 45–74 °C, with optimum growth at 60–65 °C. The pH range for growth of the strains was pH 4.6–8.0, with optimum growth at pH 7.0. The DNA G+C contents of strains ONI-1T and ONI-5T were 60.2 and 58.1 mol%, respectively. The major fatty acid was iso-C17 : 0 and the major menaquinone was MK-9(H2). The cell walls of the strains contained glutamic acid, serine, glycine, histidine, alanine and ornithine. The polar lipids consisted of phosphatidylinositol, phosphatidylglycerol and a glycolipid. The cell-wall sugar was rhamnose. Detailed phylogenetic analysis based on 16S rRNA gene sequences indicated that the strains belong to the class Ktedonobacteria and that strains ONI-1T and ONI-5T are most closely related to Thermosporothrix hazakensis SK20-1T (85.3 and 84.5 % sequence similarity, respectively). 16S rRNA gene sequence similarity between the two strains was 96.6 %. Based on the phenotypic features and phylogenetic position, we propose that strains ONI-1T and ONI-5T constitute a novel genus containing two novel species, for which we propose the names Thermogemmatispora onikobensis gen. nov., sp. nov. (the type species; type strain ONI-1T  = JCM 16817T  = KCTC 19768T) and Thermogemmatispora foliorum sp. nov. (type strain ONI-5T  = JCM 16818T  = KCTC 19767T), within the new family Thermogemmatisporaceae fam. nov. and order Thermogemmatisporales ord. nov.