Thermus composti sp. nov., isolated from oyster mushroom compost

A Gram-stain-negative, rod-shaped bacterium (strain K-39T) was isolated from the thermophilic phase of the composting process for oyster mushroom substrate preparation. The strain grew at 40–80 °C (optimum, 65–75 °C), at pH 5–9 (optimum, pH 7), in media containing up to 1.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain K-39T formed a distinct lineage within the genus Thermus. Its closest cultivated relative was Thermus islandicus PRI 3838T (96.8 % similarity). The DNA G+C content of strain K-39T was 71.3 mol%. The new strain could be differentiated from the related taxa by not being able to hydrolyse starch. The predominant fatty acids of strain K-39T were iso-C17 : 0 and anteiso-C17 : 0. Strain K-39T contained a lower amount of the fatty acid iso-C15 : 0 as compared to related species of the genus Thermus. The predominant respiratory quinone of the new isolate was menaquinone MK-8. On the basis of a taxonomic study using a polyphasic approach, strain K-39T is considered to represent a novel species of the genus Thermus, for which the name Thermus composti sp. nov. is proposed. The type strain is K-39T ( = DSM 21686T = NCAIM B 02340T).