地杆菌适应胞外受体多样性的电势感知通路及其调节机制

微生物胞外呼吸是驱动厌氧环境中碳氮硫铁等关键元素循环的引擎。地杆菌属是土壤与沉积物中最重要的胞外呼吸菌，其最显著特征是可利用胞外受体的种类多及电势范围宽。然而，地杆菌如何“感知”胞外受体的电势高低并调控代谢行为，机制尚不清楚。本项目基于地杆菌胞外电子传递链可以耦联“胞内Arc系统”与“胞外受体”的认识与推测，提出“地杆菌电势感知通路及调节机制”的科学设想，期望揭示地杆菌感知与响应受体电势的分子机制。选取硫还原地杆菌为代表菌种、水钠锰矿和水铁矿为典型受体、水稻土为典型土壤，系统研究地杆菌感知电势信号自“胞外受体→胞外电子传递链→Arc系统”的传导途径，解析电势感知通路的组成、结构及其转导电势信号过程，探明地杆菌依赖电势感知通路响应不同受体电势的分子机制，揭示实际土壤环境中地杆菌适应多种受体的调控策略。电势感知通路的揭示，不仅对胞外呼吸基础理论至关重要，而且有助于开创新型土壤原位修复技术。

Microbial extracellular respiration drives the global cycling of some key elements, such as C, N, S, Fe et al., in anaerobic environments. Geobacter species are the most important extracellularly respiring microorganisms in soil and sediment, and their most distinctive feature is the broad spectrum of electron acceptors with a wide electrochemical window. However, how Geobacter species first sense potential of electron acceptors and then accordingly regulate extracellular respiration is unknown. Considering the extracellular electron transport chain can couple the inner-membrane “Anoxic Redox Control (Arc) system” with an “extracellular electron acceptor”, we propose a process of “extracellular electron acceptor redox potential sensing and subsequent gene regulation” in Geobacter species. Here, we will provide evidences supporting this process and demonstrate the underlying molecular mechanisms. The type strain Geobacter sulfurreducens will be selected to study its sensory and regulatory response to the two different electron acceptors ferrihydrite and birnessite. In addition, we will also study the sensory and regulatory response of Geobacter species in paddy soil to different environmental redox potentials. We will first focus on the signal transduction pathway from extracellular electron acceptor via the extracellular electron transport chain to the Arc system. The composition, structure and signal transduction mechanism of the Arc system will be elucidated. Subsequently, the extracellular electron acceptor redox potential-sensing pathway and its mechanism of action on the regulation of extracellular respiration will be solved. Our study will broaden the knowledge on microbial extracellular respiration, and provide a new strategy that can be used for in situ bioremediation of soil.