Two Gram-staining-positive, strictly aerobic bacilli, designated as strains Ma50-5T and Ma50-6T, were isolated from the hydrothermal sediments of Manus Basin in the western Pacific Ocean. Based on 16S rRNA gene sequence, strains Ma50-5T and Ma50-6T were most closely related to Bacillus alveayuensis (97.0 and 97.2 % identity, respectively). The 16S rRNA gene sequence identity between strains Ma50-5T and Ma50-6T was 97.4 %. The identities between strains Ma50-5T and Ma50-6T and other closely related organisms were below 97.0 %. The G+C contents of the genomic DNA of strains Ma50-5T and Ma50-6T were 43.4 and 47.6 mol%, respectively. The major fatty acids (>10 %) of both strains were iso-C15 : 0 and iso-C17 : 0. The predominant isoprenoid quinone detected in both strains was menaquinone-7. Phylogenetic, physiological, biochemical and morphological analyses suggested that strains Ma50-5T and Ma50-6T represent two novel species of the genus Bacillus, for which the names Bacillus kexueae sp. nov. (type strain Ma50-5T=KCTC 33881T=CCTCC AB 2017020T) and Bacillus manusensis sp. nov. (type strain Ma50-6T=KCTC 33882T=CCTCC AB 2017019T), respectively, are proposed.
Keywords: Bacillus; hydrothermal vent; new species; taxonomy; thermophilic.