赤杆菌(Erythrobacter atlanticus)的多环芳烃趋化受体蛋白及趋化机制研究

The degradation of polycyclic aromatic hydrocarbons (PAHs) by marine bacteria is the main way to resolve marine PAHs pollution. Study of PAHs biodegradation has been focusing on the degradation pathway. However, the understanding of the chemotaxis mechanism is still very limited. The sensing and chemotactic process of bacteria to PAHs is the very first step of PAHs biodegradation. Chemotaxis greatly affects the efficiency of PAHs uptake and actively participates in the PAHs degrading regulation. Erythrobacter was one of the predominant PAHs-degrading bacteria in the ocean. Erythrobacter atlanticus, a novel strain isolated from deep-sea sediment of the Atlantic Ocean, can efficiently degrade many types of PAHs. Despite of its chemotactic ability to PAHs, E. atlanticus does not contain any homologous gene of the known chemotaxis receptor protein, which is an important element in the classic chemotaxis system. This project intends to investigate the molecular mechanism of the chemotaxis of E. atlanticus to PAHs using a series of techniques such as PAHs induction, RNA-seq, random mutagenesis screening, bioinformatics analysis, site-directed mutagenesis and complementation verification. We plan to explore the chemotaxis receptor protein of E. atlanticus to PAHs, analyze the chemotaxis signal transduction pathway and the associated regulation pathway. Our goal is to discover a new chemotaxis mechanism to PAHs, to advance our knowledge of the molecular mechanism of the biodegradation of PAHs, and to provide novel foundation for a better understanding of the contribution of deep-sea microorganisms to the self-restoration process of polluted environment.

微生物降解是环境多环芳烃污染物清除的重要途径。细菌降解多环芳烃的研究一直集中于降解途径的分析，对其趋化机制的认识还很缺乏。感应与趋化是细菌降解多环芳烃的第一步，关系着细菌摄入多环芳烃的效率，也参与了多环芳烃的降解调控。赤杆菌（Erythrobacter）是海洋环境中的优势多环芳烃降解菌之一。分离自大西洋深海沉积物的赤杆菌新种E. atlanticus能高效降解多种多环芳烃，但初步研究发现该菌基因组中不具备任何经典趋化系统中的甲基受体趋化蛋白等关键基因，却有多环芳烃趋化行为。本项目拟通过多环芳烃诱导表达、转录组分析、随机突变库筛选、生物信息学预测、定点突变和回补验证等一系列手段探寻E. atlanticus的多环芳烃趋化受体蛋白，解析其趋化信号的转导和调控过程。预期将发现新的多环芳烃趋化机制，为深入理解多环芳烃的细菌代谢机制、认识微生物在环境自净中的作用提供理论基础。

趋化机制是细菌感应环境的第一步，它不但参与了细菌的运动调控，也参与了细菌的其他代谢过程，对理解细菌与环境的相互作用有重大意义。然而目前对PAHs降解细菌的趋化系统研究还比较粗浅。本项目通过胶囊持续释放PAHs的方式高效诱导赤杆菌（Erythrobacter）的差异性表达基因，并结合分子生态网络分析等生物信息学的手段，发现了赤杆菌的趋化受体蛋白PCPY2，通过定点突变、毛细管实验、BLi生物膜干涉等技术，进行了结合能力和趋化能力验证，并进一步发掘了这个新的趋化体系的CheY2、PAS、双组份系统等关键基因，提出了可能的调控网络。在缺失经典甲基受体趋化蛋白的赤杆菌中，本研究发现了新的趋化机制，为深入理解PAHs细菌代谢调控机制提供理论基础。同时，本研究发现的趋化受体蛋白在PAHs污染物的监测和分离方面，也有潜在的应用价值。