Extracellular Comparative Proteomics Research For S. Mutans With Different Cariogenicity

Streptococcus mutans is considered as a major etiological factor of dental caries, also proved having close relationship with many systemic diseases. Extracellular proteins, always contain pathogenic or toxic factors, are closely related to the pathogenesis of the disease. A variety of high-throughput omics technology are widely used in the study of Streptococcus mutans.Previous studies have found that tooth decay, rarely life-threatening,but it is still an important public health problem. In order to reduce the incidence of dental caries, the understanding of microbial cause caries is important. Tooth surface is covered with a layer of biofilm-which contains hundreds of millions of bacteria, polymers, saliva and food debris. The matured biofilm, also known as dental plaque, provide a perfect survival environment for many of oral bacterias.The first part construction of caries modelS. mutans adhered to tooth surface, and finally formed the dental plaque biofilm.Followed by, the acidogenicity, aciduricity make strong cariogenicity. Through the establishment of the hydroxyapatite adhesion model, we verify that the S. mutans especially clinical isolates have different cariogenicity. A standard, repeatable rat model were established for subsequent experiments.The second part extracellular comparative proteomics research for S. mutans with different cariogenicityWe measured the growth of streptococcus mutans curve. Precipitation extracellular proteins by TCA method. Two-dimensional electrophoresis and mass spectrometry were used to analyse the precipitated proteins. Through the result of mass spectrometry analysis, we finally locked the SI, SacB two protein. Their extracellular protein at two-dimensional electrophoresis with significant differences in expression. The diference may be the key factors which lead to differences of cariogenicity.The third part Streptococcus mutans SI, SacB protein expression and purificationWe first tested the expression level of S1, sacB gene. qRT-PCR results showed SI, SacB in high cariogenicity strains were highly expressed at the process of transcription<= Then, we constructed the pET-28a-S1, pET-28a-sacB recombinant expression vectors, finally, we expressed and purified S1 protein. The function of S1, sacB proteins need to be further studied.