变形链球菌ComCDE密度感应参与不同菌种的竞争

Quorum sensing system is involved in bacteriocin production and bacterial competition of Streptococcus mutans

目的研究口腔变形链球菌(S.mutans)ComCDE密度感应系统参与血链球菌(S.sanguinis)的相互竞争作用。方法采用LIVE\DEADBacLightTM荧光染色结合激光共聚焦显微镜,观察变形链球菌(简称变链菌)在CSP信号肽诱导下群体细菌自身死亡变化;通过荧光定量反转录聚合酶链反应(RT-PCR)测定细菌素以及细菌素免疫蛋白相关基因表达变化,分析变链菌ComCDE系统参与菌群生存竞争的调控机制。结果在细菌竞争中,变形链球菌ΔcomC、ΔcomD、ΔcomE突变株失去不同菌种间的竞争力,无法抑制相邻S.sanguinis的正常生长;只有野生株保持竞争力,抑制相邻S.sanguinis生长,形成缺陷菌环。CSP信号肽诱导下,变链菌群体死菌/活菌率增高58.1%(P<0.05);细菌素及免疫蛋白相关SMU.151、SMU.423、SMU.1913c基因分别升高23.3倍(P=0.00)、15.9倍(P<0.05)、19.3倍(P<0.05)。结论变形链球菌ComCDE密度感应系统调控变链菌的变链素及免疫蛋白产生、参与不同菌种间竞争生存。

Objective To study the role of ComCDE quorum sensing system of Streptococcus mutans （S.mutans） in bacteriocin production and bacterial competition. Methods Growth competition between S.mutans and Streptococcus sanguis （S.sanguis） was analyzed through the bacterial competition assay. Cellular growth and death of S. mutans with and without CSP peptide was monitored by using the laser confocal microscopy and LIVE/DEAD BacLightTM staining. Bacteriocin and bacteriocin immunity protein related gene expression was determined by real-time RT-PCR. Results Competition assay showed that S.mutcms 5comC, AcomD, and z^comE mutant lost the ability of competition, and they could not suppress the normal growth of S.sanguinis, while S.mutans UA159 wild type strain inhibited the normal growth of the adjacent S.sanguinis. In the presence of CSP peptide, the ratio of Dead/live cells of S.mutans UA159 was increased 58.1% （P 〈 0.05）, and bacteriocin and immunity protein related genes SMU.151, SMU.423, and SMU.1913c, were increased 23.3-fold （P=0.00）, 15.9-fold （P〈 0.05）, and 19.3-fold （P 〈 0.05） respectively. Conclusion Quorum sensing system of S.mutans is involved in bacteriocin production and bacterial competition.