Genome-based reclassification of Peribacillus castrilensis Rodríguez et al. 2023 as a later heterotypic synonym of Peribacillus frigoritolerans (Delaporte and Sasson 1967) Montecillo and Bae 2022, and an emended description of Peribacillus frigoritol

A comparison of 16S rRNA gene sequences between <i>Peribacillus frigoritolerans</i> DSM 8801 ^T and <i>Peribacillus castrilensis</i> N3^T revealed 99.9% sequence similarity, suggesting their close relatedness and the possibility of these strains belonging to the same species. The genus <i>Peribacillus</i> includes 21 species with validly published names. The type species <i>P. frigoritolerans</i> DSM 8801^T (=ATCC 25097^T=CCUG 43489^T=CIP 67.20^T=JCM 11681^T) was isolated from arid soil in Morocco, while <i>P. castrilensis</i> N3^T (=CECT 30509^T=LMG 32505^T) was isolated from the faeces of a river otter in Castril (Granada, southern Spain). The present study used whole-genome data to clarify the taxonomic assignment of these two closely related <i>Peribacillus</i> species. <i>P. frigoritolerans</i> DSM 8801^T and <i>P. castrilensis</i> N3^T share similar chemotaxonomic and phenotypic characteristics. Their main cellular fatty acids were anteiso-C_{15 : 0} and iso-C_{15 : 0}. Overall genomic relatedness indices analyses indicated that <i>P. frigoritolerans</i> DSM 8801^T and <i>P. castrilensis</i> N3^T shared average nucleotide identity and digital DNA-DNA hybridization values >95% and >70%, which are the currently accepted thresholds for species-level delineation. Additionally, these taxa formed a tight cluster within the genus <i>Peribacillus</i> in both the 16S rRNA gene phylogenetic tree and the core-genome phylogenomic tree. Based on the combined evidence and the earliest valid publication, priority is given to <i>P. frigoritolerans</i> (Delaporte and Sasson 1967) Montecillo and Bae 2022. <i>Peribacillus castrilensis</i> Rodríguez <i>et al</i>. 2023 is proposed to be a later heterotypic synonym of <i>P. frigoritolerans</i> (Delaporte and Sasson 1967) Montecillo and Bae 2022.