A Preliminary Study On The Growth Reg ? Lation Of The HtrA Gene In Deciduous Streptococcus Mutans

Objective:The aim of this study is to explore the growth regulation ability of HtrA gene in Streptococcus mutans separated from deciduous teeth and compare the difference of growth between S.mutans with HtrA high virulence and strains with HtrA deficiency under stress and non-stress environment.Methods:(1)In pre-experiment,the strains with HtrA high virulence were pre-screened and identified,and reconstructed the strains with HtrA deficiency.The strains were reanimated and incubated in anaerobic culture.After identifying the strains,use turbidity method to measure OD600 value of two strains growing in culture at 1.5h,3h,4h,6h,8h,10h,12h,24h under the non-stress and stress environment(pH 5.5,0.5MNaCl,0.0005%H2O2),then draw the growth curve of two strains under the non-stress and stress environment(pH 5.5,0.5MNaCl,0.0005%H2O2).Use MTT method to measure the OD510 of two strains growing into stationary phases(t=12h)under the non-stress and stress environment(pH 5.5,NaCl 0.5M,H2O20.0005%),and compare the difference between two strains.Results:(1)The results showed that colonies,Gram staining and biochemical identification of two strains were in line with standard biological traits of Streptococcus mutans.(2)The growth curves of two strains in non-stress environment were consistent with the typical Streptococcus mutans,but the OD600 of growth and the OD510 of the bacteria saturation of strains with HtrA deficiency were less than that of strains with HtrA high virulence,there was statistically significant difference between two strains(p<0.05).(3)The growth curve models of the two strains in stress conditions(pH 5.5,0.5MNaCl,0.0005%H2O2)were also consistent with standard growth curve.The OD600 of growth and the OD351 of live bacteria(t=12h)of strains with HtrA deficiency was less than that of strains with HtrA high virulence in acidic and oxidative environment,the difference between two strains was statistically significant(p<0.05).While in hypertonic environment(0.5MNaCl),the OD600 of growth and the OD510 of live bacteria(t=12h)of the two strains was no difference(p>0.05).Conclusion:HtrA gene,to some extent,could affect the growth ability of Streptococcus mutans separated from deciduous teeth in non-stress and stress environment(acidic stress and oxidative stress),but couldn't in hyperosmotic stress.