| Caries is a bacterium infectious disease which is harmful to human oral. The incidence of caries in our country is high, which makes the prediction and prevention of this disease particularly important. At present ,there is no accurate and effective forecasting methold, and traditional metholds are mainly through detecting the number of the main cariogenic bacteria (serotype C streptococcus mutans) to predict the risk of caries of individuals. As the limitation in this prediction methold, many studies showed that the number of streptococcus mutans is not the only determining factor in the process of caries, but the different cariogenic ability of strains is an important factor. Clearly, studying the difference of the cariogenic ability between streptococcus mutans strains may provide new ideas of forecasting the caries.To study the differences of the cariogenic ability between streptococcus mutans strains and to study the reasons, our issue team had been successfully separated the streptococcus mutans clinical strains 593 and 18 from caries-active and caries-free individuals and confirmed that the cariogenic ability between these two strains is different after a series of in-vitro experiments.In this study, based on the results of preliminary studies, the differences between proteome of strain 593 and that of strain 18 was compared to investigate the cause of different cariogenic potential of streptococcus mutans strains. This study has included two parts:Part I: the differences of proteome between the serotype C streptococcus mutans clinical strains isolated from caries-active and caries-free individuals by SDS-PAGE Methods: differences of cellular and extracellular soluble protein expression between 593 stain and 18 stain was compared by SDS-PAGE.Results: In cellular soluble protein electrophoresis, specific band about 75 KDa was observed in 593 strain; The differences of protein expression amount in about 85, 60, 50, 40KDa between 593 strain and 18 strain were observed. In extracellular soluble protein electrophoresis, specific bands about 75 KDa and 40 KDa were observed in 593 strain; specific band about 50 KDa was observed in 18 strain; The difference of protein expression amount in about 60KDa between 593 strain and 18 strain was observed.Conclusion: It is indicated that a significant difference existed between the proteome of strains 593 and 18. The difference may contribute to the different cariogenic potential of these two strains.Partâ…¡: the differences of the surface-associated proteins between the serotype C streptococcus mutans clinical strains isolated from caries-active and caries-free individuals at different pH by electrophoresisMethods: the surface-associated proteins were extracted from 593 strain and 18 strain at pH7.0 and pH5.0, then differences of these proteins expression between two strains and between different pH were compared by SDS-PAGE,2-DE and MALDI-TOF MS.Results: In surface-associated protein electrophoresis of two strains,extracted at pH 7.0, specific bands, six specific spots and four different expression spots about 110, 38, 36 KDa were observed in 593 strain; different expression band, two specific spots and four different expression spots about 28KDa were observed in 593 strain. After analying three of these spots by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS),we found that the expression of glycosyltransferase in 593 strain was high and the expression of ABC transporter, pyruvate kinase were specific.In surface-associated protein electrophoresis of two strains, extracted at pH 7.0 and pH 5.0, same pecific bands, same specific spots and same different expression spots of two strains between pH 7.0 and pH 5.0 were observed. But pecific band about 75 KDa was only observed in 593 strain at pH 5.0, six specific spots and four different expression spots were only observed when 593 strain was grown at low pH. After analying five of these spots by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS) ,we found that the expression of 3-glyceraldehyde-phosphate dehydrogenase, two-component system histidine kinase in 593 strain were high and the expression of signal histidine kinase subtype, LPS biological synthesis of protein, NADH oxidase were specific.Conclusion: 1 A significant difference was existed between the surface-associated proteins of strains 593 and 18 at pH 7.0 .The difference may contribute to the different cariogenic potential of these two strains. 2 Following growth at pH 5.0, the acid reaction of two strains were observed. The same change of protein expression about two stains were observed. But the different change of protein expression was observed in 593 strain. This difference may contribute to the different acid resistance potential of these two strains.
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