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

描述(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。环境感知中的一个重要机制是趋化性，这是一种负责细菌游泳方向变化的两组分信号通路。最近，通过对专性厌氧病原菌肉毒梭菌和破伤风梭菌的基因组分析，鉴定了甲基接受趋化蛋白(MCP)与血红素一氧化氮/氧(H-NOX)传感器结构域的融合。H-NOX结构域广泛存在于生物学中，存在于从细菌到哺乳动物的各种生物体中。对配体结合的分子理解已经建立起来。然而，这些结构域在专性厌氧细菌中的信号传播机制仍不清楚。以前描述的气体感受性趋化蛋白对气体有间接反应。例如，大肠杆菌中的氧感应器Aer可以随着氧浓度的变化而感知胞质还原电位的变化。H-NOX-MCP可能是一种迄今尚未确定的直接气体传感器，其中H-NOX结构域与少量配体结合，并在细菌中诱导恐慌性逃避反应。在本研究计划中，H的信号输出和配体灵敏度 NOx-MCP蛋白将在氧气或一氧化氮存在的情况下进行研究。为了了解信号传递的机制，还将研究H-NOX和MCP结构域之间的分子相互作用。最后，将对生孢子梭菌的野生型和H-NOX-MCP突变体进行体内趋化实验，以了解该生物体对稳步增加的氧气和一氧化氮浓度的反应。这项研究将扩大对细菌双组分信号转导的了解，并表征一种新的有毒气体传感机制，这种机制与梭状芽孢杆菌的致病物种相同。

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.