Helicobacter pylori: Tactic Responses and Persistence in the Gastric Mucosa

描述（由申请人提供）：胃肠道粘膜病原体必须穿透黏液层，以建立下层粘膜上皮的感染。我们的研究解决的基本生物学问题是，粘膜定植是随机的，还是指导这一过程的遗传特征的功能。我们正在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。我们假设幽门螺杆菌对胃液局部酸度的变化反应迅速，通过动力相关的化学感受器，监测胃酸的时间变化；（ii）酸性pH趋向性对细菌的初始定植和持久性至关重要，使细菌能够摆脱极端的酸性胁迫。为了验证这一假设，我们开发了几种pH趋向性试验，在这些试验中，幽门螺杆菌对酸（而不是碱）表现出阴性的趋化反应，而在这些试验中，非胃种肝门螺杆菌和空肠弯曲杆菌没有pH趋化反应。我们确定了新的化学受体TIpB是pH趋向性和胃定植所必需的。为了进一步验证pH趋向性假说，我们提出了以下具体目标：（目的一）通过缺失其他三个化学受体基因来分离TIpB功能，验证TIpB功能，确定酸阈值和TIpB与其他Tips的相对丰度，并通过筛选胃和非胃种幽门螺杆菌来确定TIpB和酸感是否为胃种所特有；（Aim II） TIpB含有独特的周质和HAMP结构域，这些结构域可能参与酸感知，删除和定点突变扫描将用于确定哪些结构域感知酸（周质或细胞质），以及关键组氨酸或其他氨基酸的质子化是否需要信号转导；（目的III）我们建议确定脲酶系统（pH停滞）和全局反应调节因子ArsRS和HP1043（酸胁迫）如何与快速酸性pH策略行为相结合，从而指导酸生存、胃定植和终生持续。相关性：值得注意的是，幽门螺杆菌可以在100毫米盐酸中存活并表现出酸性pH的亲和性，这是迄今为止研究过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.