Compare Of Genomes And Proteins Between Fluoride-resistant Strains And Their Parental Strains Of Streptococcus Mutans And Streptococcus Sobrinus

The rationale for the caries preventive effect of fluoride has been known for many decades.The fact that fluoride can be incorporated into the crystalline lattice of the mineral of the dental hard tissues,resulting in a tissue less soluble in acid environment,has been the scientific cornerstone for caries prevention. But using the fluoride for long-term may lead to appearance of the Fluoride-Resistant Strain. Through the technology of the SDS-PAGE and the REA AP-PCR, we wanted to know whether the genomes and the proteins had change significantly in the Fluoride-Resistant mutation of the Streptococcus mutans and Streptococcus sobrinus. Finally, this research provided an advantageous experiment evidence for the mechanism of the appearance of the Fluoride-Resistant Strain.Part I: Induction of the Fluoride-resistant strain of Streptococcusmutans and Streptococcus sobrinusThe Fluoride-resistant strains of Streptococcus mutans and Streptococcus sobrinus were induced in vitro by gradient increasing the concentration of NaF (from Oug/ml to 1000/ml). The Fluoride-resistant strains obtained can be cultured in the medium with fluoride (1000g/ml NaF) or without fluoride. The Fluoride-resistant strains are reliable experiment models, which can be used in further studies of the mechanism of fluoride-resistant.Part II:Compare of genomes and proteins between fluoride-resistant strains and their parental strains of Streptococcus mutans and Streptococcus sobrinus1. To investigate the genome changes between Fluoride-resistant strains and their parental strains, AP-PCR was applied. The results showed that the DNA amplification bands between Fluoride-resistant strains and parental strains were completely different. Compared to parental strains, some DNA bands disappeared, but some new bands were observed in Fluoride-resistant strains. Their DNA fingerprints were also different. The results suggest that the genomes of Fluoride-resistant strains have changed.2. REA was also used to analyze the difference between Fluoride-resistant strains and their parental strains. Genomes of both Fluoride-resistant strains and their parental strains were digested by restriction endonucleases and analyzed by agarose gel electrophoresis. The results showed that the types, amounts and distributions of endonucleases sites were all different between Fluoride-resistant strains and their parental strains. The results confirmed that the genomes of Fluoride-resistant strains have changed.3. Bacteria contain several of proteins, which take part in all kinds of life activities of bacteria. To investigate the difference between Fluoride-resistant strains and their parental strains, proteins of all this strains were analyzed by SDS-PAGE. The results showed the protein files of Fluoride-resistant strains and their parental strains were completely different.All the above results demonstrate that the genomes of Fluoride-resistant strains have changed, some genes mutated. The Fluoride-resistant strains have obtained some new genome characteristics compared to their parental strains.Part III: Measurement of the growth suppression effect of Chorhexidine on the Fluoride-resistant strains and their parental strains of Streptococcus mutans and Streptococcus sobrinusA new question was raised because of the appearance of the Fluoride-resistant Streptococcus mutans and Streptococcus sobrinus-how to suppress the Fluoride-resistant strains? The growth suppression effect of Chorhexidine was measured in this study. The acetic acid chlorhexidine was diluted into different concentrations, and added to Fluoride-resistant strains and their parental strains. The MIC and MBC of each strain were measured. The results showed that Chlorhexidine could suppress growth of all kinds of strains including Fluoride-resistant strains in 350g/ml, and kill all kinds of strains in 400g/ml. The results demonstrate that Chlorhexidine is very effective reagent to suppress the growth of the Streptococcus mutans, Streptococcus and Fluor...