Host adapted N-metabolism of Listeria monocytogenes

单核增生李斯特菌是一种兼性的人类细胞内病原体，13c同位素谱分析（IPA）已被应用于巨噬细胞和上皮细胞复制过程中的碳代谢。在第二个资助期，拟开展一个研究该革兰氏阳性模式生物体内氮代谢的项目。具体而言，将确定主要氮源，并研究n代谢途径，包括脱氨后各自碳骨架的命运。该结果有望提高我们对植物适应宿主生态位过程中氮代谢的认识。通过我们团队的分析和微生物工具和专业知识，将解决三个核心问题：(i)在巨噬细胞和秀丽隐杆线虫感染期间，单核增生乳杆菌的n来源是什么？（ii）这些来源是如何在单核增生乳杆菌的中枢代谢中降解和利用的？（三）哪些基因缺失会特别中断这些代谢通量？通过定量磁共振（NMR）光谱和质谱（MS），将在体外测定从底物到李斯特菌的代谢通量。这种方法将扩展到巨噬细胞和线虫在15N-和15N/ 13c双标记化合物存在下的感染实验。将感染15N/ 13c预标记的细胞或线虫，以确定在这些条件下从宿主到细菌的代谢途径和通量。IPA将应用于第一期资助期选取的单核增生乳杆菌突变体或对乙醇胺和其他n源利用不足的突变体。在这里确定的关键氮代谢反应中有缺陷的突变体的毒力将在小鼠感染模型中进行测试。

L. monocytogenes is a facultative intracellular human pathogen which 13C-isotopologue profiling analysis (IPA) has been applied to with a focus on carbon metabolism during replication in macrophages and epithelial cells. For the 2nd funding period, a project is proposed that will study the in vivo nitrogen (N) metabolism of this Gram-positive model organism. Specifically, main nitrogen source(s) will be identified, and the pathways of N-metabolism including the fate of the respective carbon backbones after deamination will be studied. The results are expected to improve our understanding of the listerial N metabolism during its adaptation to host niches. By the analytical and microbiological tools and expertise of our groups, three central questions will be addressed: (i) Which are the N-sources for L. monocytogenes during infection of macrophages and Caenorhabditis elegans? (ii) How are these sources degraded and utilized in the central metabolism of L. monocytogenes? (iii) Which gene deletions specifically interrupt these metabolic fluxes? By quantitative magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), metabolic fluxes from substrates to listeriae will be determined in vitro. This approach will be extended to infection experiments with macrophages and nematodes in the presence of 15N- and 15N/13C-doubly labeled compounds. 15N/13C-prelabeled cells or nematodes will be infected to determine the metabolic pathways and fluxes from the host to the bacterium under these conditions. IPA will be applied to selected mutants of L. monocytogenes from the 1st funding period or those defective in the utilization of ethanolamine and other N-sources. The virulence of mutants defective in key nitrogen metabolic reactions as determined here will be tested in a mouse infection model.