Reclassification of Paenibacillus frigoriresistens Ming et al. 2012 as a later heterotypic synonym of Paenibacillus alginolyticus (Nakamura 1987) Shida et al. 1997.

In this study, the taxonomic relationship between Paenibacillus frigoriresistens and Paenibacillus alginolyticus was reassessed utilizing a polyphasic taxonomic approach. Molecular identification through 16S rRNA gene sequence analysis demonstrated that P. alginolyticus DSM 5050^T exhibited the highest sequence similarities with Paenibacillus phytorum LMG 31458^T (99.57%), Paenibacillus germinis LMG 31460^T (99.28%), P. frigoriresistens YIM 016^T (99.07%) and Paenibacillus planticolens LMG 31457^T (98.49%). Phylogenetic analyses based on both 16S rRNA gene sequences and whole-genome sequences revealed that P. alginolyticus DSM 5050^T clustered with P. frigoriresistens YIM 016^T, suggesting a close relationship between these two strains. Moreover, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between them were 97.33 and 76.90%, respectively, surpassing the recommended species delineation thresholds of 95-96% for ANI and 70% for dDDH. These results indicated that P. alginolyticus and P. frigoriresistens belonged to the same genomic species. This conclusion was further supported by phenotypic and chemotaxonomic characteristics. According to the data above, we propose that P. frigoriresistens Ming et al. 2012 is a later heterotypic synonym of P. alginolyticus (Nakamura 1987) Shida et al. 1997.