Helicobacter pylori: Tactic Responses and Persistence in the Gastric Mucosa

描述（由申请方提供）：胃肠道的粘液病原体必须穿透粘液层，以建立下层粘膜上皮的感染。我们的研究所要解决的基本生物学问题是，粘膜定植是随机发生的，还是遗传性状的作用决定了这一过程。我们使用人类胃病原体幽门螺杆菌作为模型系统来研究粘膜定植。我们假设H.幽门螺杆菌反应迅速，在胃粘液中的局部酸度的变化，通过运动相关的化学感受器，监测胃酸的时间变化;和（ii）酸性pH值的的士是必不可少的主要殖民地和持久性，使细菌逃避极端的酸压力。为了验证这一假设，我们已经开发了几种pH趋药性测定法，其中H。pylori对酸（而不是对碱）显示阴性趋化反应，并且在这些测定中，非胃物种H.肝菌和空肠弯曲菌不是pH趋化菌。我们确定，新的化学感受器TIpB需要的pH值的趋化性和胃定植。我们提出了以下具体目标来进一步检验pH趋化性假说：（目的I）通过删除其他三个化学感受器基因来分离TIpB功能以验证TIpB功能，确定TIpB和其他Tips的酸阈值和相对丰度，并通过筛选胃和非胃螺杆菌物种来确定TIpB和酸敏感是否为胃物种所特有;（目的II）TIpB含有独特的周质和HAMP结构域，其可能参与酸传感，并且缺失和定点突变扫描将用于鉴定哪些结构域感测酸。（周质或细胞质）以及信号转导是否需要关键组氨酸或其它氨基酸的质子化;（目的III）我们提出确定尿素酶系统（pH停滞）和全局响应调节剂ArsRS和HP 1043（酸应激）如何与快速酸pH策略行为在指导酸存活、胃定植和终身持久性中相互作用。相关性：值得注意的是，H。幽门螺杆菌可以在100 mM盐酸中存活并显示酸性pH趋化性，这是迄今为止研究的任何微生物病原体都无法比拟的壮举。了解与酸存活和胃定植相关的基本机制是所有根除策略的基础，从疫苗到针对感染世界一半人口的病原体的新疗法。

DESCRIPTION (provided by applicant): Mucosal pathogens of the gastrointestinal tract must penetrate layers of mucus in order to establish infection of the underlying mucosal epithelium. The fundamental biological question our research addresses is whether mucosal colonization is by random chance or a function of genetic traits that direct the process. We are using the human gastric pathogen Helicobacter pylori as a model system to study mucosal colonization. We hypothesize that H. pylori responds rapidly to changes in local acidity in gastric mucus, through motility-linked chemoreceptors, that monitor temporal changes in gastric acidity; and (ii) that acid pH taxis is essential for primary colonization and for persistence by enabling bacteria to escape extreme acid stress. To test this hypothesis we have developed several pH taxis assays in which H. pylori displays negative chemotactic responses to acids (not to bases) and in these assays non-gastric species H. hepaticus and Campylobacter jejuni are not pH tactic. We determined that novel chemoreceptor TIpB is required for both pH taxis and for gastric colonization. We propose the following specific aims to further test the pH taxis hypothesis: (Aim I) To isolate TIpB function by deletion of the three other chemoreceptor genes to validate TIpB function, determine acid thresholds and the relative abundance of TIpB and other Tips and by screening gastric and non-gastric species of Helicobacter to determine whether TIpB and acid sensing are unique to gastric species; (Aim II) TIpB contains unique periplasmic and HAMP domains that might participate in acid sensing and both deletion and site directed mutagenesis scanning will be used to identify which domains sense acid (periplasmic or cytoplasmic) and whether protonation of key histidine or other amino acids is required for signal transduction; (Aim III) We propose to determine how the urease system (pH stasis) and global response regulators ArsRS and HP1043 (acid stress) interface with rapid acid pH tactic behavior in directing acid survival, gastric colonization and life long persistence. Relevance: It is remarkable that H. pylori can survive and display acid pH taxis in 100 mM hydrochloric acid, a feat unmatched by any microbial pathogen studied to date. Understanding the fundamental mechanisms associated with acid survival and gastric colonization underpins all eradicative strategies from vaccines to novel therapeutics against a pathogen that infects half of the world's population.