Membrane vesicle heterogeneity of Streptococcus mutans is associated with strain-specific cariogenicity

Background Streptococcus mutans (S. mutans) is a major etiological agent of dental caries, and pronounced heterogeneity in cariogenic phenotypes exists among different strains. The membrane vesicles (MVs) of S. mutans participate in biofilm formation, and their yield and cargo composition vary with environmental conditions. The relationship between MVs and strain-specific differences in cariogenicity remains unclear.Materials and methods The cariogenic potential of the strains was validated using a rat caries model, and strain-specific cariogenic phenotypes were correlated with MV abundance, physicochemical properties, biological functions, and proteomic composition.Results Compared with MVs from weakly cariogenic strains, those derived from highly cariogenic strains were larger in size and greater in quantity. These MVs reversed defects in biofilm formation, extracellular matrix synthesis, and acid production in UA159 ΔgtfBC. Increased exopolysaccharide synthesis and eDNA accumulation strengthened the biofilm matrix architecture and upregulated the transcription of the acidogenesis-related gene ldh in recipient bacteria. Proteomic analyses revealed that MVs from highly cariogenic strains exhibited distinct protein cargo profiles enriched in multiple virulence-associated proteins, including Gtfs.Conclusion MVs derived from S. mutans strains display clear strain‑dependent heterogeneity. The differences in physicochemical properties, secretion abundance, biological functions, and protein cargo are associated with cariogenic potential.