RNC Gene Mutation of Streptococcus Mutans Inhibits Adherence of Porphyromonas Gingivalis via Modulating FimAIV and RgpA Gene In Vitro

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Minlei Zhao, Chunhua Chen, Man Xue, Ying Lu, Yonggang Li, Ruixia Zeng, Yibo Zhang


Background: Porphyromonas gingivalis (P.gingivalis), which is involved in subgingival microbial biofilm of dental plaque, is an important causative pathogen in periodontal disease.

Objectives: to investigate the effect of Streptococcus mutans on adherence of P.gingivalis by fimbriae and gingipain R.

Methods: In vitro, S.mutans with RNC gene mutants and P.gingivalis with FimAIV or RgpA gene mutant were co-culture. P.gingivalis biofilm formation was detected by crystal violet and fluorescein-5-isothiocyanate (FITC) staining. The ability of P.gingivalis to infect human periodontal ligament fibroblasts (HPDLFs) and the expression levels of FimAIV and RgpA genes were detected by quantitative polymerase chain reaction.

Results: S.mutans RNC gene-deletion (∆RNC) strain cell-free pH-neutralized supernatant (CFS) reduced significantly the biofilm formation of P.gingivalis than S.mutans 25175-WT strain CFS. Moreover, the gingipain R (RgpA), rather than the long fimbriae (FimAIV), was involved in adhesion of P.gingivalis by lowering inhibition of ∆RNC strain CFS. In addition, S.mutans ∆RNC strain CFS inhibited the infection rate of P.gingivalis W83 in HPDLFs by reducing the gene-expression levels of FimAIV and RgpA. However, Neither S.mutans ∆RNC and 25175-WT strains cells or CFS reduced the infection rate of P.gingivalis ∆FimAⅣ strain in HPDLFs.

Conclusions: the ∆RNC gene of S.mutans was involved in inhibiting P.gingivalis W83 biofilm formation through affecting the important virulence factors (FimAIV and RgpA) of P.gingivalis in biofilm formation and infection in HPDLFs elucidated. Thus, it elucidated ∆RNC S.mutans strains can be considered a potential strain to prevent P.gingivalis induced periodontitis.

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