Reclassification of Brevibacterium frigoritolerans DSM 8801T as Bacillus frigoritolerans comb. nov. Based on Genome Analysis

Abstract

16S rRNA gene sequence analysis showed that the type strain Brevibacterium frigoritolerans DSM 8801^T had the highest similarity (99.7%) with the reference strain Bacillus simplex NBRC 15720^T, followed by Bacillus muralis DSM 16288^T (99.6%), Bacillus butanolivorans DSM 18926^T (99.5%), and Bacillus loiseleuriae FJAT-27997^T (97.9%). This relationship is confirmed by the phylogenetic analysis indicating that Bre. frigoritolerans DSM 8801^T fell in the genus Bacillus group and formed a clade with the closely related Bacillus species. Average nucleotide identity and in silico DNA-DNA hybridization (isDDH) values between strain DSM 8801^T and the most closed reference strain Bac. simplex NBRC 15720^T were both much lower than species definition threshold values of 95% and 70%, respectively, which indicated strain DSM 8801^T should not be affiliated to one of the validly named Bacillus species. The percentage of conserved protein (POCP) values between the strain DSM 8801^T and the type strains of the above species were 80.7%, 69.2%, 72.2%, 53.6%, and 50.0%, respectively, higher than the genus definition threshold value of 50%. The main isoprenoid quinone of strain DSM 8801^T was MK-7, the main polar lipids were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), and phosphatidyl ethanolamine (PE), and the major fatty acids were anteiso-C_15:0 and iso-C_15:0. On the basis of the phenotypic, chemotaxonomic, phylogenetic and genomic characteristics, Bre. frigoritolerans DSM 8801^T should belong to the genus Bacillus, and be proposed to reclassify as Bacillus frigoritolerans comb. nov., with the type strain DSM 8801^T (=ATCC 25097^T = CCUG 43489^T = CIP 67.20^T = JCM 11681^T).