Streptococcus lishijunsis sp. nov. isolated from feces of Apodemus Chevrieri in western china and its genome function analysis

Two gram-positive, non-motile, and α-hemolytic streptococci strains, zg-JUN1979T and zg-JUN1980, were isolated from the feces of Apodemus chevrieri in Weining County, Guizhou Province, China. This study aimed to characterize these strains through polyphasic taxonomy and genomic taxonomy, determine their taxonomic classification within the genus Streptococcus. The strains were analyzed using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), 16 S rRNA gene sequencing, whole-genome sequencing (Illumina NovaSeq X Plus), average nucleotide identity (ANI), and digital DNA-DNA hybridization (dDDH). Phenotypic traits were assessed via Biolog GEN III, API 50CH, and API ZYM assays, while chemotaxonomic analysis included fatty acid profiling, polar lipid characterization, and respiratory quinone detection. Genomic functional potential was evaluated using the Comprehensive Antibiotic Resistance Database (CARD), Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), Non-Redundant protein (NR), Pathogen-Host Interaction Database (PHI), and Virulence Factor Database (VFDB). Phylogenetic analysis based on 16 S rRNA gene sequences revealed 97.35% similarity to Streptococcus hyointestinalis NCTC 12,224T, with distinct clade separation. Whole-genome sequencing confirmed analysed strains as conspecific (ANI = 98.99%, dDDH = 90.6%), but both diverged significantly from S. hyointestinalis (ANI = 72.01%, dDDH = 20.6%). Phenotypically, analysed strains uniquely utilized gentiobiose, sucrose, and α-ketoglutaric acid. Chemotaxonomic analysis identified predominant fatty acids C14:0 (30.8%) and C16:0 (34.1%), a polar lipid profile including diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), and absence of respiratory quinones. The genome G + C content was 40.06 mol%. Genomic analysis revealed reduced virulence factors (e.g., defective urease activity) alongside antibiotic resistance genes, suggesting a mixed commensal-pathogenic profile. Based on molecular, phenotypic, and chemotaxonomic evidence, we propose Streptococcus lishijunsis sp. nov. (zg-JUN1979T = CGMCC 1.65027T = GDMCC 1.5474T = JCM 3776T) as a novel species. Its genomic features indicate adaptation for colonization rather than invasive infection, highlighting ecological and potential clinical implications for wildlife-associated streptococci.