Bacillus thermophilum sp. nov., isolated from a microbial fuel cell

A novel thermophilic, Gram-staining positive bacterium, designated DX-2(T), was isolated from the anode biofilm of a microbial fuel cell. Cells of the strain were oxidase positive, catalase positive, facultative anaerobic, motile rods. The isolate grew at 30-60 °C (optimum 50 °C) and pH 5-9 (optimum pH 8-8.5). The pairwise 16S rRNA gene sequence similarities showed that strain DX-2(T) was most closely related to Bacillus fumarioli LMG 17489(T) (96.2 %), B. firmus JCM 2512(T) (96.0 %) and B. foraminis DSM 19613(T) (95.7 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain DX-2(T) formed a cluster with B. smithii (95.5 %) and B. infernus (94.9 %). The genomic G+C content of DX-2(T) was 43.7 mol%. The predominant respiratory quinone was MK-7. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and unknown phospholipids. The major cellular fatty acid was iso-C16:0. Based on its phenotypic characteristics, chemotaxonomic features, and results of phylogenetic analysis, the strain was identified to represent a distinct novel species in the genus Bacillus, and the name proposed is B. thermophilum sp. nov. The type strain is DX-2(T) (=CCTCC AB2012194(T) = KCTC 33128(T)).