Inhibitory effect of Streptococcus mutans antisense vicK RNA regulating the cariogenicity of oral streptococci multi-species biofilm

Abstract

Objective: To investigate the regulative effects of Streptococcus mutans (Sm) antisense vicK RNA (ASvicK) on the multi-species biofilm formed by three common oral streptococci (Sm, Streptococcus sanguinis, and Streptococcus gordonii) (Sm+Ss+Sg). Methods: ASvicK over-expression strain was constructed by using a recombinant plasmid, and three-species biofilm UA159+Ss+Sg and ASvicK+Ss+Sg were cultured. The phenotypes of biofilms were detected by scanning electron microscopy (SEM). Crystal violet (CV) assay was used to detect biofilm biomass. Lactate kit and anthrone-sulfuric acid colorimetric assay were used to determine the abilities of lactic acid and exopolysaccharides production, respectively. The proportions of three-species and expression levels of the cariogenic-related genes in biofilms were detected by TaqMan fluorescence quantitative PCR and real-time fluorescence quantitative PCR. A biofilm demineralization model of human enamel slabs was further constructed, and the hardness of enamel surface was detected. Results: Compared to UA159+Ss+Sg, over-expression of ASvicK could inhibit biofilm formation and lactic acid production in ASvicK+Ss+Sg biofilm significantly decreased by 78.93% (P<0.001) and 62.23% (P<0.001), respectively. With ASvicK over-expression, the amounts of water-insoluble and-soluble glucoses in ASvicK+Ss+Sg biofilm were reduced respectively by 39.13% (P<0.001) and 68.00% (P<0.001). Compared to the UA159+Ss+Sg Group, the proportion of Sm, the cariogenic bacteria, showed 33.00% reduction (P<0.01) in Sm+Ss+Sg biofilm, and the gene expressions of cariogenic-relative genes vicK/X, gtfB/C/D, and ftf significantly decreased (P<0.05). The micro-hardness value of enamel slabs after demineralization by ASvicK+Ss+Sg biofilm was significantly increased to 183.84% (P<0.001). Conclusions: ASvicK over-expression could reduce the Sm proportion and weaken the cariogenicity of oral Streptococcus biofilm, thereby possibly slowing down the progression of caries.