Streptococcus mutans Membrane Vesicles, Containing Insoluble Glucan Synthase and Extracellular DNA, Contribute to the Promotion of Initial Attachment and Colonization of Actinomyces oris

Abstract

Oral biofilms contribute to oral infectious diseases such as dental caries and periodontal disease. Actinomyces oris, an initial attachment colonizer, uses fimbriae（FimA, FimP, and FimQ）presented on the surface layer of the bacteria for biofilm formation. Streptococcus mutans, a cariogenic bacteria, produces membrane vesicles（MVs）with insoluble glucan synthases（GtfB and GtfC）and extracellular DNA（eDNA）. These MVs promote biofilm formation. However, few reports are available on the relationship between S. mutans-produced MVs and A. oris. Herein, the authors investigated the effect of S. mutans-produced MVs on the initial attachment and colonization（INAC）, and biofilm formation of A. oris. MVs at a final concentration of 3.125 µg/mL promoted the INAC formation of WT, ΔfimA, ΔfimP, and ΔfimQ of A. oris. However, MVs from S. mutans ΔgtfBC, lacking insoluble glucan synthase, did not induce the INAC formation in A. oris wild type and mutants. Deoxyribonuclease inhibited INAC formation of A. oris WT and ΔfimA produced by MVs. This study indicated that S. mutans-produced MVs induced fimbriae-independent INAC formation of A. oris via insoluble glucan synthase. The formation of insoluble glucan-dependent INAC in A. oris via S. mutans-produced MVs may result from the interaction between A. oris type 1 fimbriae with eDNA from MVs, potentially contributing to the stabilization of the INAC structure.