Quorum sensing system in Helicobacter pylori infection

从TN2DNA片段(DRS Ogura&Berg的Kind Gift)中经PCR扩增的LuxS：：CAT基因自然转化幽门螺杆菌TK1402菌株，获得LuxS突变株(HP06)。用哈维氏弧菌BB170菌株(巴斯勒博士赠送的礼物)通过发光生物测定来评估AI-2的产生。幽门螺杆菌luxS基因可在大肠杆菌中表达，其基因组序列与已报道的26695株和J99株的luxS基因同源性分别为96.1%和96.2%。HP06突变株的AI-2产量是TK1402亲本菌株的近百分之一。虽然HP06和TK1402的耐酸性和粘附性无显著差异，但其运动能力明显弱于TK1402。将大约109CFU的幽门螺杆菌经口接种到蒙古沙土鼠(MGS/Sea，雄性，8wk)体内，每隔24小时接种两次。在感染HP06的5只沙土鼠中，1只在感染后1个月检测到幽门螺杆菌。反之，所有感染TK1402的沙土鼠(n=5)均检测到Hp。仅在感染TK1402的沙土鼠胃粘膜中观察到严重的炎症反应，提示幽门螺杆菌的群体感应对幽门螺杆菌在沙土鼠胃粘膜的定植具有重要意义。LUXS突变体的感染性降低可能与其运动性降低有关。

The luxS mutant (HP06) was generated by natural transformation of PCR-amplified luxS::cat gene from TN2 DNA fragment (kind gift from Drs Ogura & Berg) into H. pylori TK1402 strain. The production of AI-2 was evaluated by luminescence bioassay using Vibrio harveyi BB170 strain (kind gift from Dr Bassler). luxS gene of H. pylori could be expressed in E. coli, and genome sequence of the luxS from TK1402 strain was shown to have 96.1% and 96.2% homology to that of luxS of two reported strains 26695 and J99 strains, respectively.Microbiological characteristics of 1uxS mutant HP06 strain was analyzed. The production of AI-2 by HP06 mutant was nearly one-hundredth of that by TK1402 parent strain. Although there was no significant difference in acid-resistance and adhesion activity to gastric epithelial cells between HP06 and TK1402 strains, the motility of HP06 was significantly weaker than that of TK1402. Approximately, 10^9CFU of H. pylori were orally inoculated into Mongolian gerbil (MGS/Sea, male, 8wk) twice with 24 hr-interval. H. pylori was detected by RT-PCR in 1 out of 5 HP06-infected gerbils at 1 month after infection. In contrast, H. pylori was detected by RT-PCR in all the TK1402-infected gerbils (n=5). Severe inflammation in gastric mucosa was observed only in TK1402-infected gerbil.These results indicate that quorum sensing in H. pylori is important for colonization of H. pylori in gastric mucosa of Mongolian gerbil. The decrease of infectivity by luxS mutant was implied to be associated with the decreased motility.