Department of Endodontics, Ninth People's Hospital, Shanghai Key Laboratory of Stomatology, School of Medicine, Shanghai Jiao Tong University, No. 639 Zhizaoju Road, Shanghai 200011, China.
Sensors (Basel). 2012;12(5):6155-75. doi: 10.3390/s120506176. Epub 2012 May 10.
AI-2-mediated quorum sensing has been identified in various bacteria, including both Gram-negative and Gram-positive species, and numerous phenotypes have been reported to be regulated by this mechanism, using the luxS-mutant strain. But the AI-2 production process confused this regulatory function; some considered this regulation as the result of a metabolic change, which refers to an important metabolic cycle named activated methyl cycle (AMC), caused by luxS-mutant simultaneously with the defect of AI-2. Herein we hypothesized that the quorum sensing system--not the metabolic aspect--is responsible for such a regulatory function. In this study, we constructed plasmids infused with sahH and induced protein expression in the luxS-mutant strain to make the quorum-sensing system and metabolic system independent. The biofilm-related genes were investigated by real-time polymerase chain reaction (PCR), and the results demonstrated that the quorum-sensing completed strain restored the gene expression of the defective strain, but the metabolically completed one did not. This evidence supported our hypothesis that the autoinducer-2-mediated, quorum-sensing system, not the AMC, was responsible for luxS mutant regulation.
AI-2 介导的群体感应已在各种细菌中被发现，包括革兰氏阴性和革兰氏阳性菌，并且已经报道了许多表型受到这种机制的调节，使用 luxS 突变株。但是 AI-2 的产生过程混淆了这种调节功能；一些人认为这种调节是代谢变化的结果，这指的是一个重要的代谢循环，名为激活甲基循环（AMC），由 luxS 突变株同时引起，伴随着 AI-2 的缺陷。在此，我们假设群体感应系统——而不是代谢方面——负责这种调节功能。在这项研究中，我们构建了含有 sahH 的质粒，并在 luxS 突变株中诱导蛋白表达，使群体感应系统和代谢系统独立。通过实时聚合酶链反应（PCR）研究了生物膜相关基因，结果表明，群体感应完成的菌株恢复了缺陷菌株的基因表达，但代谢完成的菌株没有。这一证据支持了我们的假设，即 AI-2 介导的群体感应系统，而不是 AMC，负责 luxS 突变体的调节。
