Biophysical determinants of chemotaxis in Helicobacter pylori

项目摘要 由可移动的细菌种类幽门螺杆菌的感染是由趋化性促进的，这种趋化性 指的是向有利的化学环境迁移的能力。幽门螺杆菌感染是一个主要原因 消化性溃疡和胃癌。然而，幽门螺杆菌趋化的生物物理机制尚不清楚。 明白了。在规范的趋化网络中，化学感受器感知细胞外配体并调节 趋化蛋白激酶的活性。该激酶反过来调节鞭毛功能，以偏向细菌迁移。至 防止网络在配基检测时变得不敏感-Cher和Cheb两种酶，连续 重置该蛋白的活性。这种重置(适应)增加了配体感测的动态范围 没有这个网络，细胞就不能继续向上或向下迁移化学梯度。然而，幽门螺杆菌 缺乏雪儿和切布的同源基因。此外，幽门螺杆菌的运动模式与标准模型不同， 大肠埃希氏菌，因为幽门螺杆菌将它们所有的鞭毛定位在一个极--单个细胞向前游(跑) 向后(反向)，而不是像大肠杆菌那样奔跑和翻滚。这种在运动性上的细微差别是 预测会导致规范框架中的多重趋化性错误。因此，当前的机械论 趋化作用的模型不能解释幽门螺杆菌有偏向和无错误的迁移。没有一个基本的 了解幽门螺杆菌的趋化性，针对趋化性的抗菌药物的开发将有可能 仍然是有限的。在拟议的工作中，PI的主要目标是解释趋化网络是如何 调节鞭毛功能以促进幽门螺杆菌的趋化作用。私家侦探的长期目标是利用洞察力 从拟议的工作中开发通过抑制趋化性来预防幽门螺杆菌感染的创新方法。 PI将使用一种新的技术，通过允许对鞭毛进行量化来克服现状 在不探测单个鞭毛马达的情况下发挥作用。通过光学镊子的组合，相位 显微镜和随机建模，PI将确定如何在单个 幽门螺杆菌的细胞和种群水平。该团队将率先开发新的分析方法，包括FRET 实验测定幽门螺杆菌的趋化信号。PI还将确定Key的角色 被认为在趋化适应中起主要作用的偶联蛋白。除了……之外 建立幽门螺杆菌趋化性的生物物理原理，预计将有以下回报：1)a) 将为理解其他运行逆转物种的趋化迁移建立范例，2)新的 趋化适应的机制可能被阐明，3.基于FRET的检测将被开发， 这将大大促进目前在该领域了解化学感受器功能和趋化性的努力 幽门螺杆菌的信号机制。这些项目的成功执行将使重大进展成为可能，因为 在大多数细菌物种中，趋化策略仍然知之甚少。

Project Abstract Infections by the motile bacterial species, Helicobacter pylori, are promoted by chemotaxis, which refers to the ability to migrate towards favorable chemical environments. H. pylori infections are a major cause of peptic ulcers and gastric cancers. Yet, the biophysical mechanisms of chemotaxis in H. pylori are not understood. In the canonical chemotaxis network, chemoreceptors sense extracellular ligands and regulate the activity of a chemotaxis kinase. The kinase in turn modulates flagellar functions to bias bacterial migration. To prevent the network from desensitizing upon ligand-detection, two enzymes, CheR and CheB, continuously reset the kinase activity. Such resetting (adaptation) increases the dynamic range of ligand sensing in the network, without which the cell cannot continue migrating up or down chemical gradients. However, H. pylori lack CheR and CheB homologues. Also, the pattern of motility in H. pylori is different from the standard model, Escherichia coli, since H. pylori localize all their flagella at a single pole – individual cells swim forward (run) and backward (reverse), rather than running and tumbling as E. coli do. This subtle difference in motility is predicted to give rise to multiple chemotaxis errors in the canonical framework. Hence, current mechanistic models of chemotaxis are unable to explain biased and error-free migration in H. pylori. Without a fundamental understanding of chemotaxis in H. pylori, the development of antibacterials that target chemotaxis will likely remain limited. In the proposed work, the PI’s primary goal is to explain how the chemotaxis network modulates flagellar functions to promote chemotaxis in H. pylori. The PI’s long term goal is to use the insights from the proposed work to develop innovative methods to prevent H. pylori infections by inhibiting chemotaxis. The PI will make use of a novel technique that overcomes the status quo by allowing quantification of flagellar functions without probing individual flagellar motors. Through a combination of optical tweezers, phase microscopy, and stochastic modeling, the PI will determine how chemotaxis errors are prevented at a single cell and population level in H. pylori. The team will pioneer the development of novel assays, including a FRET assay, to experimentally measure chemotaxis signaling in H. pylori. The PI will also determine the role of key coupling proteins that have been hypothesized to play a major role in chemotaxis adaptation. In addition to establishing the biophysical principles of chemotaxis in H. pylori, the following payoffs are anticipated: 1) a paradigm will be established for understanding chemotaxis migration in other run-reversing species, 2) novel mechanisms of chemotaxis adaptation are likely to be elucidated, 3. a FRET-based assay will be developed, which will significantly boost current efforts in the field to understand chemoreceptor functions and chemotaxis signaling mechanisms in H. pylori. Successful execution of the projects will enable a major advance since chemotaxis strategies remain poorly understood in a large majority of bacterial species.