luxS mutant regulation: quorum sensing impairment or methylation disorder?
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.
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. qtdc1010@sjtu.edu.cn
Qian
Q
Wang
Zhiyan
Z
He
Yuejian
Y
Hu
Yuntao
Y
Jiang
Rui
R
Ma
Zisheng
Z
Tang
Jingping
J
Liang
Zheng
Z
Liu
Zhengwei
Z
Huang
D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015153:Blotting, Western; D013437:Carbon-Sulfur Lyases / Q000235:genetics*; D019175:DNA Methylation; D017931:DNA Primers; D009154:Mutation; D010957:Plasmids; D053038:Quorum Sensing; D060888:Real-Time Polymerase Chain Reaction
D001426:Bacterial Proteins; D017931:DNA Primers; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria