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

描述（由申请人提供）：细菌病原体具有复杂的机制来感知和避免化学危害。环境感知的一个重要机制是趋化性，这是一种双组分信号通路，负责细菌游泳的方向变化。最近，通过专性厌氧病原体肉毒梭菌和破伤风梭菌的基因组分析，鉴定了融合到血红素一氧化氮/氧（H-NOX）传感器结构域的甲基接受趋化蛋白（MCP）。从细菌到哺乳动物，H-NOX结构域在生物中无处不在。对配体结合的分子理解已经建立。然而，这些结构域在专性厌氧细菌中的信号传播机制尚不清楚。先前表征的气敏趋化蛋白间接响应气体。例如，大肠杆菌中的氧传感器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可以作为一种迄今为止尚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诱导细菌的恐慌逃避反应。在本研究计划中，H

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.