植物乳杆菌AY01 luxS基因表达模式与功能的研究

The Research of Expression Pattern and Function of Lactobacillus plantarum AY01 luxS Gene

植物乳杆菌(Lactobacillus plantarum)是发酵食品中常见的一种益生菌,群体感应(quorum sensing,QS)是细菌进行信号交流的一种普遍方式,Lb.plantarum是否通过QS介导着其益生特性尚不清楚。为了探索Lb.plantarum AY01是否通过AI-2/LuxS QS系统介导其对常见食源性病原菌的抑制,首先运用半定量PCR方法,研究了AY01在不同生长阶段luxS基因(合成QS信号分子AI-2的关键基因)的表达情况;然后,利用牛津杯抑菌法研究了AY01对食源性病原菌肠出血性大肠杆菌(enterohemorrhagic Escherichia coli,EHEC)O157:H7、单核细胞增生李斯特菌(Listeria monocytogenes)和金黄色葡萄球菌(Staphylococcus aureus)的抑菌效果。研究发现:1)Lb.plantarum AY01 luxS基因在指数早期没有表达,指数中期出现表达,指数末期表达量明显增加,并于稳定中期达到最大值;2)AY01培养上清液对EHEC O157:H7、L.monocytogenes、S.aureus均有抑菌效果,抑菌效果与luxS基因表达趋势一致,即随AY01生长时间的增加抑菌呈现增加变化,到稳定期达到最大抑菌效果。结果表明,Lb.plantarum AY01可能通过AI-2/LuxS QS系统介导其对常见食源性病原菌的抑制。

Lactobacillus plantarum is one of the common probiotics in fermented foods;quorum sensing （QS） is a common communication way within bacteria. It is not clear that the probiotic properties of Lb. plantarum is mediated by QS. In order to explore whether Lb. plantarum AY01 mediates inhibition to common food-borne pathogens through AI-2/LuxS QS system, semi-quantitative PCR method was first used to study the expression at different growth stages of AY01 luxS gene （The key gene for synthesizing QS signal molecules AI-2）;Then, the effects of AY01 inhibition to food-borne pathogens enterohemorrhagic Escherichia coli （EHEC） O157： H7,Listeria monocytogenes and Staphylococcus aureus were studied by Oxford cup antibacterial method. The study found that： 1） Lb. plantarum AY01 luxS gene did not expressed at the early exponential phase,expression was appeared at the middle exponential phase, significantly increased at the late exponential phase, and reached a maximum level at middle stationary phase;2） The supernatant of AY01 had bacteriostatic effect to EHEC O157：H7,L.monocytogenes and S.aureus. Furthermore,the inhibitory effect had the same trend with the luxS gene expression level, which meant that the inhibitory effect was increased coupled with the growth of AY01 and arrived a maximum inhibition level at middle stationary phase. The results showed that Lb. plantarum AY01 may mediate its inhibition to the common food-borne pathogens through AI-2/LuxS QS system.