[S5-5] Bacterial survival strategies by metabolites of oral microbial populations
Extracellular membrane vesicles (MVs) invoved in glucosyltransferases (Gtfs) and suface protein atigen c (PAc) from Stretococcus mutans induce the Gtfs-dependent biofilm formation of not only S. mutans but also early colonizers on the surface, such as S. mitis, S. oralis, S. gordonii and Actinomyces sp. Oral microbial population on tooth surface may be formed by MVs produced from oral bacteria in low pH condition. In contrast, oral microorganisms produce metabolites such as short-chain fatty acids (SCFAs) and regulate pH in dental plaques. To clarify the relationship between SCFAs and biofilm formation, effects of SCFAs on the initial attachment and colonization (INAC) assay using Actinomyces orais, which is early colonizaer on the tooth surface, was investigated. INAC assays using A. oris were performed with SCFAs (acetic, butyric, propionic, valeric and lactic acids) or a mixture of them. Among the SCFAs, acetic, butyric and propionic acids and a mixture of acetic, butyric and propionic acids induced the type 1 and type 2 fimbriae-dependent and independent INAC by live A. oris. The main effects might be dependent on the levels of the non-ionized acid forms of the SCFAs in acidic stress conditions. SCFAs produced from oral microbial population after fermentation affect the INAC-associated activities of the A. oris during non-ionized acid formations in the dental plaque.