LuxS基因缺失对变异链球菌生物学性状的影响

LuxS gene mutation affects biological characteristics and biofilm formation of Streptococcus mutans

目的:观察LuxS基因突变对变异链球菌生物性状的影响。方法:将变链菌标准株和LuxS突变株分别培养于TSA、TSA-Cmr、BHI培养基培养48 h,通过菌落形态观察、常规生化检测、革兰染色涂片观察和生长曲线,比较两种菌株的生长特性;体外建立LuxS基因突变株和标准株的生物被膜模型,结晶紫染色,观察比较两菌株形成生物被膜的能力。结果:在含氯霉素的TSA-Cmr固体培养基中增塑,标准株基本不能生长,而突变株的生长状况基本正常。在不含氯霉素的TSA固体培养基中培养,两种菌株的菌落形态没有明显差别,革兰染色镜下观察,可见标准株菌体呈长链状排列且相互缠绕,而突变株菌体多呈短链状排列,形成长链的较少。生长曲线观察发现:两菌株在生长模式上基本一致,均呈典型的"S"型曲线,只是在进入生长的稳定期后,两者在细菌饱和度上有一定差异,即11.5～22.5 h之间各时间点标准株的A值均明显高于LuxS突变株(P<0.05)。在BHI培养基中两菌株均能形成生物被膜,但结构存在差异:标准株形成光滑且均匀分布的生物被膜,而突变株的生物被膜形态较粗糙。结论:LuxS基因突变对变异链球菌的生长以及生物被膜形成能力等生物学性状有一定影响。

AIM：To observe the biological characteristics and biofilm formatin properties of LuxS mutant strain of Streptococcus mutans.METHODS：Streptococcus mutans wild strain and LuxS mutant strain were cultured in TSA,TSA-Cmr and BHI respectively for 48h.The biological characteristics of the two strains were observed by colony formation,Gram-staining,routine biochemistry test and the growth curve.Biofilm formation properties of the two strains were compared through crystal violet dye method.RESULTS：Wild strain could not grow on TSA-Cmr solid medium containing chloromycetin,while LuxS mutant strain showed normal growth.When grown on TSA-Cmr solid medium without chloromycetin,colony morphology of the two strains showed no difference.When observed under a microscope,the wild strain presented a long catenation and relatively twisting form while the LuxS mutant strain presented a short catenation form.No significant difference was observed in the growth curve of the two strains except that the A values of the wild strain in stationary phase was higher than that of the mutant strain（P〈0.05）.Both strains could form biofilm on BHI medium.However,the biofilm of the LuxS mutant strain showed a very rough appearance,while the wild strain showed a relatively smooth,confluent layer.CONCLUSION：Luxs mutation can inhibit the growth of Streptococcus mutans and affect the architecture of biofilm.