Thermus composti sp nov., isolated from oyster mushroom compost

A Gram-stain-negative, rod-shaped bacterium (strain K-39(T)) was isolated from the thermophilic phase of the composting process for oyster mushroom substrate preparation. The strain grew at 40-80 degrees C (optimum, 65-75 degrees 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-39(T) formed a distinct lineage within the genus Thermus. Its closest cultivated relative was Thermus islandicus PRI 3838(T) (96.8% similarity). The DNA G + C content of strain K-39(T) 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-39(T) were iso-C-17:0 and anteiso-C-17:0. Strain K-39(T) contained a lower amount of the fatty acid iso-C-15:0 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-39(T) is considered to represent a novel species of the genus Thermus, for which the name Therm us composti sp. nov. is proposed: The type strain is K-39(T) (=DSM 21686(T)=NCAIM B 02340(T)).