The Influence Of HtrA And ClpP Gene On Oxidative Stress Of Streptococcu Mutans

Objective:To study the effect of htrA and clpP on the growth of streptococcus mutans in order to find out the differences between mutant strains and parent strain, the growth models of the standard strain, the htrA gene mutant strain, the clpP gene mutant strain and the htrA-clpP gene mutant strain were built.In order to compare the difference of the growth characteristic between the Streptococcus mutans parent strain and the mutant strains when they were cultivated under oxidative stress.Methods:The streptococcus mutans parent strain and htrA(high temperature requirement A)、clpP (caseinolytic protease P)、htrA-clpP gene mutant strains were cultured respectively in TPY medium and TPY containing H2O2concentrations0.0005%under microaerophili condition at37℃.The growth curve of each stain was determined by Thermo Labsystems. Results:1. Growth cycle of the mutant strains changed in TPY medium.The exponential phase shortened and the mutant strain grew faster than parent strain (P<0.05).The parent strain grew faster than the mutant strain during the stationary phase, the differences were statistically significant (P<0.05),the growth value of the mutant strains at24h were lower than parent strain.2. In TPY medium containing H2O2concentrations0.0005%, the mutant strains were more sensitive to oxidative stress,the parent strain grew faster than mutant strains at every growth phase; Both strains grew slower in TPY medium containing0.0005%H2O2, the differences were statistically significant (P<0.05); The clpP-htrA gene mutant strain grew more slowly than the clpP gene or htrA gene mutants, the differences were statistically significant (P<0.05).Conclusion:In our studies, despite whatever the two gene were knockouted, the growth of mutant strains were all inhibited. Compared with Streptococcus mutans parent strain, inactivate of htrA and clpP gene can influent the the capacity of Streptococcu mutans to oxidative stress.