Comparative Characterization Reveals Conserved and Divergent Ecological Traits of Oral Corynebacteria

Abstract

Corynebacteria are abundant members of the oral microbiome and increasingly recognized as key structural organizers of supragingival biofilms. Despite their prevalence, the ecological roles and phenotypic traits of many oral corynebacterial species remain poorly defined. Here, we isolated and characterized two new strains, Corynebacterium durum JJ2 and Corynebacterium argentoratense MB1, and compared them with reference strains Corynebacterium durum JJ1 and Corynebacterium matruchotii ATCC14266. Phenotypic assays revealed that C. durum strains displayed robust aggregation, thick biofilm formation, and extensive extracellular polymeric substance (EPS) networks, whereas C. argentoratense and C. matruchotii formed thinner biofilms with minimal EPS production. All four strains secreted extracellular membrane vesicles (EMVs) capable of inducing chain elongation in Streptococcus sanguinis, underscoring a conserved interspecies signaling function. Genomic analysis demonstrated close relatedness between C. durum and C. matruchotii, while C. argentoratense was more distantly related, with a reduced genome, fewer metabolic pathways, and absence of nitrate reductase genes, consistent with its inability to grow under anaerobic conditions. These findings suggest that C. argentoratense may represent a less specialized or transient inhabitant of the oral cavity, whereas C. durum and C. matruchotii are well adapted to the oral niche. Together, this study expands our understanding of phenotypic diversity, metabolic capacity, and interspecies interactions among oral corynebacteria, highlighting their potential importance as biofilm organizers and contributors to oral microbial ecology. ImportanceOral Corynebacteria contribute to the structural and ecological stability of supragingival communities. Yet, their species-level functions remain poorly defined. By isolating and characterizing new strains of Corynebacterium durum and Corynebacterium argentoratense, and comparing them with reference strains including C. matruchotii, we provide new insight into their phenotypic diversity, metabolic capacity, and ecological roles. Our results demonstrate that C. durum strains form robust biofilms enriched in extracellular polymeric substances, while C. argentoratense produces thinner biofilms and lacks the genomic features required for anaerobic growth, suggesting a less specialized or transient role in the oral cavity. Importantly, we show that extracellular membrane vesicles secreted by all tested strains promote chain elongation in Streptococcus sanguinis, highlighting a conserved mechanism of interspecies communication. These findings advance our understanding of how oral corynebacteria contribute to biofilm organization and microbial homeostasis, and position them as critical but understudied players in oral microbial ecology.