The role of quorum sensing system in Helicobacter pylori infection

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Quorum sensing (QS) is a cell-to-cell communication system that regulates bacterial phenotypes, including the expression of virulence factor genes. Helicobacter pylori is associated with gastric disorders in humans and some experimental animals, and possesses the luxS/type 2 autoinducer (AI-2) system. We examined the effects of a specific luxS mutation on the characteristics of H. pylori. On 0.3% agar medium, motility of H. pylori HPKY08 (luxS::cat) was significantly lower than that of wild-type H. pylori TK1402. The luxS-complemented strain HPKY21 exhibited motility comparable to that of H. pylori TK1402. It was shown that the luxS/M-2 system plays an important role in H. pylori motility. The luxS mutant exhibited a reduced infection rate relative to the wild-type parent strain TK1402 in a Mongolian gerbil model. At 3 months after oral inoculation, lower numbers of H. pylori were detected by qRT-PCR in luxS mutant-infected gerbils than in TK1402-infected gerbils. On other pathogenesis factor, adherence to gastric epithelial cells, acid tolerance, survival rate in macrophage like-cells, there was no significant differences between wild type and mutant strains. In both strains, 3-5 polar flagella were observed on electron microscopy. In DNA micro-array using mRNA of both strains at logarithmic phase, 53 genes including flagella associated gene in mutant strain which was 1.5 or more fold expression comparing with wild type strain. In stationary phase, lower expression data of flaA and flaB in luxS mutant than that in wild type by qRT-PCR. By 2D-SDS analysis amount of FlaB in luxS mutant strain was lower than that in wild type strain, significantly.