htrA、clpP基因缺失对变异链球菌生长影响的初步观察

Effect of htrA and clpP Mutation on the Growth of Streptococcus Mutans

目的：研究htrA、clpP基因缺失对变异链球菌生长情况的影响。方法：采用浊度法测定变异链球菌标准株、htrA单基因缺陷株、clpP单基因缺陷株及htrA—clpP双基因缺陷株生长6h中每小时的吸光度，采用MTT实验测定4种菌株的不同时间甲臌吸光度变化情况并探究其与平板计数活菌量之间的关系。结果：在正常营养条件下，浊度法1．6h及MTr法2、4h及6h变异链球菌标准株的生长快于htrA、htrA—clpP缺陷株（P〈0．01）；浊度法1-6h及MTT法1-3hclpP缺陷株生长快于其他两种缺陷株（P〈0．01）；变异链球菌标准株、htrA缺陷株及htrA—clpP缺陷株1～4h、clpP缺陷株1-3h甲脱吸光度与活菌量呈正相关（r分别为0．860、0．761、0．790及0．773，P〈0．05或P〈0．01）。结论：htrA、clpP单独或同时缺失可抑制变异链球菌的生长，MTT实验可在一定时间和一定菌数范围内反映标准株与3种缺陷株的活菌数。

Objective： To study the effect of high temperature requirement A （htrA） and easeinolytie protease P （elp P） on the growth of streptococcus mutans. Methods： The nephelometer method was used to measure the absorbanee of the culture medium each hour in six hours including the streptococcus mutans standard strain, htrA, elpP, and htrA-elpP mutant strains. MTT method was used to detect the absorbance of formazan at different time points, and calculate the linear relation between those and quantity of living bacterium measured by viable plate count. Results： In the normal nutrition condition, the growth of streptococcus mutans standard strain was significantly higher than that of the mutant strains of htrA and htrA-elpP detected by nephelometer method in 1-6 h and MTT method in 2 h and 4 h （P 〈 0.01）. The growth of elpP mutant strain was significantly higher than that of other two mutant strains using nephelometer method in 1-6 h and MTT method in 1-3 h （P 〈 0.01）. For streptococcus mutans standard strain, htrA and htrA-clpP mutant strains in 1-4 h and clpP mutant strain inl-3 h, absorbance of formazan was positively related to the concentration of the bacteria （r = 0.860, 0.761, 0.790 and 0.773, P 〈 0.05 or P 〈 0.01）. Conclusion： In this study, streptococcus mutans were inhibited by htrA or elpP deletion simul- taneouly and respectively. MTT method was used to gain the quantity of living bacterium of four strains in the range of the specific bacterial count and in a given duration.