Bacillus composti sp nov and Bacillus thermophilus sp nov., two thermophilic, Fe(III)-reducing bacteria isolated from compost

Two novel thermophilic bacteria, designated SgZ-9(T) and SgZ-10(T), were isolated from compost. Cells of the two strains were catalase-positive, endospore-forming and Gram-staining-positive rods. Strain SgZ-9(T) was oxidase-positive and non-motile, and strain SgZ-10(T) was oxidase-negative and motile. The highest 16S rRNA gene sequence similarity for both strains SgZ-9(T) and SgZ-10(T) was observed with Bacillus fortis (97.5 % and 96.9 %, respectively). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain SgZ-9(T) formed a cluster with B. fortis R-6514(T) and Bacillus fordii R-7190(T), and SgZ-10(T) formed a cluster with Bacillus farraginis R-6540(T). The DNA-DNA pairing studies showed that SgZ-9(T) displayed 41.6 % and 30.7 % relatedness to the type strains of B. fortis and B. fordii, respectively. The 16S rRNA gene sequence similarity between strains SgZ-9(T) and SgZ-10(T) was 97.2 %, and the level of DNA-DNA relatedness between them was 39.2 %. The DNA G+C content of SgZ-9(T) and SgZ-10(T) was 45.3 and 47.9 mol%, respectively. Chemotaxonomic analysis revealed that both strains contained the menaquinone 7 (MK-7) as the predominant respiratory quinone. The major cellular fatty acids (>5 %) were iso-C-15:0, anteiso-C-15:0, anteiso-C-17:0, iso-C-16:0 and iso-C-17:0 in SgZ-9(T) and iso-C-15:0, anteiso-C-15:0, iso-C-17:0, anteiso-C-17:0 and iso-C-16:0 in SgZ-10(T). Based on the phenotypic characteristics, chemotaxonomic features, DNA-DNA hybridization with the nearest phylogenetic neighbours and phylogenetic analysis based on the 16S rRNA gene sequences, the two strains were determined to be two distinct novel species in the genus Bacillus, and the names proposed are Bacillus composti sp. nov. SgZ-9(T) (=CCTCC AB2012109(T)=KACC 16872(T)) and Bacillus thermophilus sp. nov. SgZ-10(T) (CCTCC AB2012110(T)=KACC 16873(T)).