Molecular Basis and Regulatory Mechanisms of Bacterial Interspecies and Intercellular Interactions

微生物几乎总是存在于微生物群落中。群落成员之间的细胞间相互作用影响着单个微生物的基因表达、活动和生存，并塑造了微生物群落的结构和功能。为了理解细菌的生命过程和理解微生物群落，如生物膜和人类微生物群，了解细菌细胞如何与邻近细胞相互作用以及它们如何调节基因和行为以响应这种相互作用是至关重要的。我的研究计划的长期目标是了解细菌种间和细胞间相互作用的分子基础和调控途径。我的研究重点是铜绿假单胞菌，一种普遍存在的革兰氏阴性细菌，可引起植物，动物和人类的严重感染。铜绿假单胞菌是研究生物膜和细菌细胞间相互作用（包括群体感应）的典型模式微生物。我们对3型分泌系统（T3SS）和6型分泌系统（T6SS）特别感兴趣，它们将效应蛋白直接传递到邻近的真核细胞或细菌细胞中，并改变或停止靶细胞中的基因表达和生理过程。T3SS和T6SS是铜绿假单胞菌种间相互作用的主要机制，但其调控机制尚不清楚。在此基础上，本研究拟进一步研究T6SS和T3SS在铜绿假单胞菌中的具体调控机制，探讨T3SS调控的、T6SS对Fem系统的影响及其在种间相互作用中的作用。本研究的短期目标是：1)研究rtcb介导的RNA修饰在T6SS调控中的作用；2)验证atp依赖性Clp蛋白酶在T6SS调控中的作用；3)阐明H3-T6SS与T3SS、pyocyanin生成、蛋白酶活性和运动之间联系的分子基础；4)表征可能介导P. aeruginosa与分枝杆菌相互作用的Fem系统的调控。意义：本研究将揭示细菌种间相互作用的分子基础和新的调控机制。RNA修饰和atp依赖性蛋白酶复合物在T3SS和T6SS调控中的作用将被表征。全球调控途径的趋同和潜在的物种间信号通路Fem系统的调控将被揭示。这些信息将有助于回答细菌如何调节其基因表达以响应其他细胞的基本问题。由于这些细胞间系统在致病性和微生物群中的关键作用，这些结果也将导致新的抗菌靶点和更好的细菌活性和微生物群落管理。

Microbes almost always exist in microbial communities. Intercellular interactions between the members of a community affect an individual microbe's gene expression, activities and survival, and shape the structure and function of the microbial community. To comprehend the bacterial life process and understand microbial communities such as biofilms and human microbiota, it is essential to know how bacterial cells interact with their neighbouring cells and how they regulate their genes and behaviours in response to such interactions. The long-term goal of my research program is to understand the molecular basis and regulatory pathways of bacterial interspecies and intercellular interactions. My research focuses on Pseudomonas aeruginosa, a ubiquitous Gram-negative bacterium that causes serious infections in plants, animals and humans. P. aeruginosa is a paradigmatic model microorganism for study of biofilms and bacterial cell-cell interaction including quorum sensing (QS). We are particularly interested in the Type 3 Secretion System (T3SS) and Type 6 Secretion Systems (T6SS) which deliver effector proteins directly into adjacent eukaryotic or bacterial cells and alter or halt gene expression and physiological processes in the targeted cells. T3SS and T6SS represent a major mechanism of interspecies interaction in P. aeruginosa, yet their regulation is not well understood. Building on our recent exciting findings, this proposed research aims to investigate the detailed regulations of T6SS and T3SS in P. aeruginosa, and to explore the T3SS-regulated, T6SS affecting Fem system and its role in interspecies interaction. The short-term objectives of the proposed research are to: 1) investigate the role of RtcB-mediated RNA modification in T6SS regulation, 2) verify the involvement of the ATP-dependent Clp protease in T6SS regulation, 3) elucidate the molecular basis underlying the connection of H3-T6SS with T3SS, pyocyanin production, protease activity and motility, and 4) characterize the regulon of the Fem system that potentially mediates interaction between P. aeruginosa and mycobacteria. Significance: The proposed research will reveal the molecular basis and new regulatory mechanisms of bacterial interspecies interactions. The role of RNA modification and ATP-dependent protease complex in the regulation of T3SS and T6SS will be characterized. Convergence of global regulatory pathways and the regulation of the potential interspecies signaling pathway Fem System will be uncovered. Such information will contribute to answering the fundamental question of how bacteria modulate their gene expression in response to other cells. Owing to the critical roles of these intercellular systems in pathogenicity and microbiota, the results will also lead to novel antibacterial targets and better management of both bacterial activities and microbial communities.