Phenotypic and genomic characterization of Paenibacillus salivarius sp. nov., isolated from the human oral cavity.

A novel Gram-stain-negative, facultatively anaerobic, endospore-forming bacterium, designated DYY-L-2T, was isolated from the saliva of a 69-year-old patient with chronic periodontitis in Hengyang, China. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain DYY-L-2T belonged to the genus Paenibacillus, with the highest similarity to Paenibacillus konsidensis LBYT (98.6%), followed by Paenibacillus vini LAM0504T (97.2%). Whole-genome sequencing yielded a complete circular chromosome of 5,642,305 bp with a genomic DNA G + C content of 50.8%. Overall genome relatedness index analysis indicated low average nucleotide identity (ANI < 80%) and in silico DNA-DNA hybridization (isDDH < 25%) values between strain DYY-L-2T and its closely related type strains, supporting its status as a novel genospecies. The strain grew optimally at 37 °C, in pH 7.0, and tolerated up to 5% (w/v) NaCl. Major cellular fatty acids were C16:0 and anteiso-C15:0. The genomic functional annotation identified unique regions enriched with mobile genetic elements and Type I restriction-modification systems (e.g. hsdR and hsdM), suggesting adaptive mechanisms for genomic stability in the oral environment. Based on polyphasic taxonomic data, strain DYY-L-2T represents a novel species within the genus Paenibacillus, for which the name Paenibacillus salivarius sp. nov. is proposed. The type strain is DYY-L-2T (= GDMCC 1.6010T = KCTC 43851T). This study expands the understanding of the Paenibacillus diversity in host-associated environments and provides insights into its ecological role in the human oral microbiome.