Symbiobacterium toebii sp. nov., commensal thermophile isolated from Korean compost

Abstract

A thermophilic nonspore-forming rod isolated from hay compost in Korea was subjected to a taxonomic study. The microorganism, designated as SC-1T, was identified as a nitrate-reducing and nonmotile bacterium. Although the strain was negatively Gram-stained, a KOH test showed that the strain SC-1T belonged to a Gram-positive species. Growth was observed between 45 and 70°C. The optimal growth temperature and pH were 60°C and pH 7.5, respectively. The G+C content of the genomic DNA was 65 mol% and the major quinone types were MK-6 and MK-7. A phylogenetic analysis based on 16S rDNA sequences revealed that the strain SC-1T was most closely related to Symbiobacterium thermophilum. However, the level of DNA-DNA relatedness between strain SC-1T and the type strain for Symbiobacterium thermophilum was approximately 30%. Accordingly, on the basis of the phenotypic traits and molecular systematic data, the strain SC-1T would appear to represent a new species within the genus Symbiobacterium. The type strain for the new species is named SC-1T (=KCTC 0307BPT; DSM 15906T).