Analysis of the Patho-Metabolism of Legionella pneumophila during Intracellular Replication

病原菌在人体内的复制是感染建立的关键事件。尽管每一种宿主与微生物的相互作用都是独一无二的，但即使是在遗传学上相距遥远的细菌也会发展出类似的策略来进入和逃离宿主细胞。然而，宿主细胞内的复制生态位对于主要的人类病原体是完全不同的。例如，军团菌、沙门氏菌和分枝杆菌居住在专门的空泡中，而弗朗西斯菌、李斯特菌和志贺氏菌则选择细胞质作为其复制生态位。因此，细胞内细菌必须使其代谢适应各自环境中遇到的可用营养素和物理条件。具体而言，泡状细菌必须科普低pH值，自由基，营养剥夺和抗菌化合物，而胞质溶胶似乎是一个更宽容的环境。直到最近，才有新的证据表明，细胞内细菌使用多种底物来有效地利用来自其宿主细胞的不同和不断变化的环境的营养供应。也有越来越多的证据表明，细菌入侵者从而引发宿主细胞代谢的重大重组，特别是在非癌症原代细胞中。因此，病原体和宿主之间的相互作用是高度动态的，导致在感染期间两种生物体的可变营养和代谢途径使用。这种宿主和病原体之间微妙的代谢相互作用最近被称为病理代谢。虽然对于细胞内细菌的成功复制至关重要，但病理代谢是细菌感染的一个相当未探索和未利用的特征。这也适用于本提案的特定主题，即嗜肺军团菌（Lp）与其宿主细胞之间的代谢关系。为了阐明细胞内Lp的病理代谢，Lp及其宿主细胞（例如巨噬细胞）的代谢组成、途径和通量将首次通过基于13 C-同位素谱、基于GC-MS和NMR的代谢组学、全细胞FT-IR和所研究菌株的生长/适合性表征的综合方法来研究。在这种综合方法的基础上，感染过程中的基本代谢模式和反应应被确定为抗菌药物开发的潜在未来目标。强调了该提案的一般主题的相关性，关于预防和控制细菌感染和耐药性的基础研究是2015年最新一届G7峰会的主要目标之一。

The replication of pathogenic bacteria inside the human host is a crucial event for the establishment of an infection. Despite the uniqueness of each host-microbe interaction, even phylogenetically distant bacteria developed comparable strategies to enter and to escape the host cell. However, the replication niche within host cells is quite different for major human pathogens. Whereas for example Legionella, Salmonella and Mycobacterium reside in specialized vacuoles, Francisella, Listeria and Shigella have chosen the cytosol as their replicative niche. As a consequence, intracellular bacteria have to adapt their metabolism to the available nutrients and physical conditions encountered in the respective environments. Specifically, vesicular bacteria have to cope with low pH, free-radicals, nutrient deprivation and antimicrobial compounds, whereas the cytosol seems to be a more permissive milieu. Only recently, there is emerging evidence that intracellular bacteria use multiple substrates to efficiently exploit the nutrient supply from the different and changing environments of their host cells. There is also increasing evidence that the bacterial invaders thereby trigger a major re-organization of the host cell's metabolism, especially in non-cancer primary cells. Consequently, the interactions between pathogens and hosts are highly dynamic resulting in variable nutrient and metabolic pathway usages of both organisms during the infection. This delicate metabolic interplay between host and pathogen was recently termed as patho-metabolism. Although crucial for the successful replication of intracellular bacteria, patho-metabolism is a quite unexplored and unexploited feature of bacterial infections. This also holds true for the specific topic of this proposal, namely the metabolic relationship between Legionella pneumophila (Lp) and its host cells. In order to elucidate the patho-metabolism of intracellular Lp, the metabolic compositions, pathways and fluxes of Lp and its host cells, e.g. macrophages, shall be studied for the first time by an integrative approach based on 13C-isotopologue profiling, GC-MS- and NMR-based metabolomics, whole-cell FT-IR, and growth/fitness characterization of the strains under study. On the basis of this comprehensive approach, essential metabolic patterns and reactions during the infection shall be identified as potential future targets for antimicrobial drug development. Highlighting the relevance of the general topic of this proposal, basic research on the prevention and control of bacterial infections and resistance was among the major goals of the latest G7 Summit in 2015.