htrA、clpP基因缺失对变异链球菌耐酸性的影响

Effect of of htrA and clpP mutation on the ability of the acid tolerance of Streptococcus mutans

目的探讨htrA、clpP基因缺失对变异链球菌耐酸性的影响。方法变异链球菌标准株及htrA缺陷株、clpP缺陷株培养至对数中期分成两组,一组作为实验组进行5h预酸化处理(pH=5.5),一组作为对照组在普通乳酪消化胨酵母(TPY)培养液中处理5h,然后将两组菌株在致死性酸环境(pH=3.0)处理3h,每隔1h取菌液采用平板活菌计数法测定活菌数,计算得到生存率,统计学分析。结果 3h内,未经预酸化处理三种菌株生存率相比差异无统计学意义(P>0.05),预酸化处理后,与标准株相比htrA缺陷株和clpP缺陷株生存率都有下降(P<0.05),两种缺陷株相比生存率差异无统计学意义(P>0.05),预酸化处理的标准株和htrA缺陷株生存率均明显高于未经预酸化处理(P<0.05),预酸化处理对生存率的影响大于两种基因分别缺失(P<0.05)。结论与变异链球菌标准株相比,htrA缺陷株和clpP缺陷株耐酸能力有不同程度的下降。

Objective To study the effect of inactivation htrA or clpP on the the acid tolerance of Streptococcus mutans.Methods Strains were grown to mid-logarithmic growth phase and devided into experimental group and control group.Experimental group was resuspended in TPY with pH 5.5 for 5 h as adapted strains.The control group was treated in TPY at pH 7.0 for 5 h as unadapted strains.Then the two groups were sustained in a lethal TPY with pH 3.0 for 3 h,the survival rate of strain was calculated every hour.All the data were statistically analyzed.Results The survival rates of the three unadapted strains was not statistically significant within 3 h（P0.05）.The viabilities of the survival rate of htrA adapted mutant strain and clpP adapted mutant strain was significantly lower than that of adapted standard stain（P0.05）.Compared with the survival rate of htrA adapted mutant strain,there were no obvious differences in the survival rate of the clpP adapted mutant strain（P0.05）.The survival rates of adapted standard strain and htrA adapted mutant strain were higher than that of the same unadapted strains（P0.05）.The effect of TPY at pH 5.5 on strain was higher than that of the two genes knockouted（P0.05）.Conclusions Compared with Streptococcus mutans standard strain,the abilities of the acid tolerance of htrA mutant strain and clpP mutant strain declined to various degrees.