Helicobacter pylori: Tactic Responses and Persistence in the Gastric Mucosa

描述(申请人提供)：胃肠道的粘膜病原体必须穿透粘液层，才能确定底层粘膜上皮的感染。我们的研究解决的基本生物学问题是，粘膜的定植是随机的，还是指导这一过程的遗传特征的函数。我们正在使用人类胃部病原体幽门螺杆菌作为一个模型系统来研究粘膜定植。我们假设，幽门螺杆菌通过与运动相关的化学感受器对胃粘液局部酸度的变化做出快速反应，该感受器监测胃酸的时间变化；以及(Ii)酸的pH趋向性对原发定植和持久性是必不可少的，使细菌能够逃避极端的酸应激。为了验证这一假说，我们发展了几种pH趋化试验，在这些试验中，幽门螺杆菌对酸(而不是碱)表现出负的趋化反应，在这些试验中，非胃种肝杆菌和空肠弯曲菌不是pH策略。我们确定新的化学感受器TiPb对于pH趋化和胃定植都是必需的。我们提出了以下具体目标来进一步验证pH趋向性假说：(目标i)通过缺失另外三个化学受体基因来分离TiPb的功能，以验证TiPb的功能，确定酸阈值和TiPb和其他Tips的相对丰度，并通过筛选胃和非胃的幽门螺杆菌物种来确定TiPb和酸感知是否是胃物种独有的；(目标ii)TiPb含有可能参与酸感知的独特的周质和HAMP结构域，并且将使用缺失和定点突变扫描来确定信号转导需要哪些结构域(周质或细胞质)以及关键组氨酸或其他氨基酸是否需要蛋白质；(目的III)我们建议确定尿素酶系统(pH停滞)和全球反应调节因子ArsRS和HP1043(酸应激)如何与快速酸pH策略行为相互作用，以指导酸生存、胃定植和终生持久性。相关性：值得注意的是，幽门螺杆菌能够在100 mM的盐酸中存活并显示出酸性pH趋向性，这是迄今为止研究过的任何微生物病原体无法比拟的壮举。了解与酸生存和胃定植有关的基本机制是所有根除战略的基础，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.