Thermosporothrix hazakensis gen. nov., sp. nov., isolated from compost, description of Thermosporotrichaceae fam. nov. within the class Ktedonobacteria Cavaletti et al. 2007 and emended description of the class Ktedonobacteria

Abstract

We isolated from compost an aerobic, thermophilic, Gram-stain-positive, spore-forming bacterium that formed branched vegetative and aerial mycelia. This strain, designated SK20-1T, grew at 31-58 degrees C, with optimum growth at 50 degrees C, while no growth was observed below 28 or above 60 degrees C. The pH range for growth was 5.4-8.7, with optimum growth at pH 7.0, while no growth was observed below pH 5.0 or above pH 9.1. Strain SK20-1T was able to hydrolyse polysaccharides such as cellulose, xylan and chitin. The DNA G+C content was 54.0 mol%. The major fatty acid was iso-C17:0 and the major menaquinone was MK-9(H2). The cell wall contained glutamic acid, serine, alanine and ornithine in a molar ratio of 1.00:1.07:2.64:0.83. The polar lipids consisted of phosphatidylinositol, phosphatidylinositol mannosides, phosphatidylglycerol, diphosphatidylglycerol and an unknown glycolipid. Cell-wall sugars were rhamnose and mannose. Detailed phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SK20-1T belongs to the class Ktedonobacteria, and that the strain is most closely related to Ktedonobacter racemifer SOSP1-21(T) (88.5 %). On the basis of its phenotypic features and phylogenetic position, we propose that SK20-1T represents a novel genus and species, Thermosporothrix hazakensis gen. nov., sp. nov., within the new family Thermosporotrichaceae fam. nov. The type strain of Thermosporothrix hazakensis is strain SK20-1(T) (=JCM 16142T =ATCC BAA-1881T). In addition, we propose an emended description of the class Ktedonobacteria to classify the class in the phylum Chloroflexi.