Competitive dynamics and balance between and commensal streptococci in oral microecology.

Dental caries, as a biofilm-related disease, is closely linked to dysbiosis in microbial ecology within dental biofilms. Beyond its impact on oral health, bacteria within the oral cavity pose systemic health risks by potentially entering the bloodstream, thereby increasing susceptibility to bacterial endocarditis, among other related diseases. , a principal cariogenic bacterium, possesses virulence factors crucial to the pathogenesis of dental caries. Its ability to adhere to tooth surfaces, produce glucans for biofilm formation, and metabolize sugars into lactic acid contributes to enamel demineralization and the initiation of carious lesions. Its aciduricity and ability to produce bacteriocins enable a competitive advantage, allowing it to thrive in acidic environments and dominate in changing oral microenvironments. In contrast, commensal streptococci, such as , , and , act as primary colonizers and compete with for adherence sites and nutrients during biofilm formation. This competition involves the production of alkali, peroxides, and antibacterial substances, thereby inhibiting growth and maintaining microbial balance. This dynamic interaction influences the balance of oral microbiota, with disruptions leading to shifts in microbial composition that are marked by rapid increases in abundance, contributing to the onset of dental caries. Thus, understanding the dynamic interactions between commensal and pathogenic bacteria in oral microecology is important for developing effective strategies to promote oral health and prevent dental caries. This review highlights the roles and competitive interactions of commensal bacteria and in oral microecology, emphasizing the importance of maintaining oral microbial balance for health, and discusses the pathological implications of perturbations in this balance.