Direct gas sensing and repellent response to toxic gases in anaerobic pathogens

描述（由申请人提供）：细菌病原体具有感知和避免化学危害的复杂机制。趋化性是环境感知的一个重要机制，是一种负责细菌游动方向变化的双组分信号通路。最近，通过对专性厌氧病原体肉毒梭菌和破伤风梭菌的基因组分析，发现了与血红素一氧化氮/氧（H-NOX）传感器结构域融合的甲基接受趋化蛋白（MCP）。H-NOX结构域在生物学中普遍存在，在从细菌到哺乳动物的生物体中发现。已经建立了对配体结合的分子理解。然而，这些结构域在专性厌氧细菌中的信号传播机制仍然未知。先前表征的气敏趋化性蛋白间接响应气体。例如，Aer，E.大肠杆菌，传感器的变化，细胞溶质的还原电位作为氧浓度的变化。H-NOX-MCP可以充当迄今为止未表征的直接气体传感器，其中H-NOX结构域结合小浓度的配体并在细菌中诱导恐慌逃避反应。 在本研究计划中，H的信号输出和配体敏感性 将在氧或一氧化氮存在下研究NOX-MCP蛋白。为了理解信号传递的机制，还将研究H-NOX和MCP结构域之间的分子相互作用。最后，将对生孢梭菌的野生型和H-NOX-MCP突变体进行体内趋化性实验，生孢梭菌是C.肉毒杆菌，以了解有机体如何应对稳步增加浓度的氧气和一氧化氮。这项调查将扩大知识的细菌双组分信号，以及表征一种新的机制，常见的致病性梭菌属的有毒气体传感。

DESCRIPTION (provided by applicant): Bacterial pathogens possess elaborate mechanisms to sense and avoid chemical hazards. One important mechanism in environmental sensing is chemotaxis, a two-component signaling pathway responsible for directional change in bacterial swimming. Recently, methyl-accepting chemotaxis proteins (MCP) fused to Heme Nitric oxide/Oxygen (H-NOX) sensor domains were identified through genomic analyses of the obligate anaerobic pathogens Clostridium botulinum and Clostridium tetani. Ubiquitous in biology, H-NOX domains are found in organisms from bacteria to mammals. A molecular understanding of ligand binding has been established. However, the signal propagation mechanisms of these domains in obligate anaerobic bacteria are still unknown. Previously characterized gas-sensing chemotaxis proteins respond indirectly to gases. For example, Aer, the oxygen sensor in E. coli, senses changes in cytosolic reduction potential as oxygen concentration changes. The H-NOX-MCP may act as a heretofore-uncharacterized direct gas sensor in which the H-NOX domain binds small concentrations of ligand and induces a panic evasion response in bacteria. In this research plan, signal output and ligand sensitivity of the H NOX-MCP protein will be investigated in the presence of oxygen or nitric oxide. To understand the mechanism of signal transmission, the molecular interactions between H-NOX and MCP domains will also be studied. Finally, in vivo chemotaxis experiments will be performed on wild type and H-NOX-MCP mutants of Clostridium sporogenes, a close relative to C. botulinum, to understand how the organism responds to steadily increasing concentrations of oxygen and nitric oxide. This investigation will expand knowledge of bacterial two-component signaling as well as characterize a novel mechanism for toxic gas sensing common to pathogenic species of Clostridium.