The intracellular metabolism of Legionella pneumophila and its regulation

嗜肺军团菌（Lp）常见于淡水栖息地，是军团菌病的病原体。虽然已经报道了Lp的各种毒力因子，但对宿主细胞适应中的细胞内营养和代谢知之甚少。我们已经通过同位素分析表明，氨基酸（例如丝氨酸）以及葡萄糖作为在培养物中生长的Lp合成氨基酸和PHB的主要碳源。与一般观点相反，我们可以证明葡萄糖是通过Entner-Doudoroff（艾德）途径代谢的，并且艾德途径对于Lp的完全体内毒力是必需的。Lp分泌一种类似真核生物的葡糖淀粉酶GamA以降解糖原和淀粉。值得注意的是，GamA在阿米巴的细胞内复制过程中是活跃的，突出了碳水化合物营养在细胞内条件下的作用。在这些结果的基础上，我们现在将使用不同的宿主分析Lp的体内代谢。本研究的目的是确定和量化的代谢物通量在适应各种主机条件。为此，将使用同位素体和代谢物分析，将研究中的所有生物体的体外数据与体内实验的数据进行比较。该分析还将包括毒性较低的菌种L。oakridgensis以及缺乏已知调节因子或细胞内代谢关键酶的Lp突变株。了解不同军团菌属的代谢策略将有助于更好地了解军团菌的适应性、毒力和持久性，并可能导致更好的方法来对抗这些病原体。

Legionella pneumophila (Lp) is commonly found in freshwater habitats and acts as the agent of Legionnaires´ disease. Although various virulence factors of Lp have been reported, less is known about intracellular nutrition and metabolism in adaptation of the host cell. We have shown by isotopologue profiling that amino acids (e.g. serine) as well as glucose serve as a major carbon source for Lp grown in culture to synthesize amino acids and PHB. In contrast to the general view, we could demonstrate that glucose is metabolized via the Entner-Doudoroff (ED) pathway and that the ED pathway is necessary for full in vivo virulence of Lp. Lp secretes an eukaryotic-like glucoamylase GamA to degrade glycogen and starch. Notably, GamA is active during intracellular replication in amoebae highlighting the role of carbohydrate nutrition under intracellular conditions. On the basis of these results, we will now analyse the in vivo metabolism of Lp using different hosts. The study is aimed to identify and to quantify the metabolite fluxes in adaptation of the various host conditions. To this end, isotopologue and metabolite profiling will be used comparing in vitro data for all organisms under study with those from in vivo experiments. The analysis will also include the less virulent species L. oakridgensis as well as mutant strains of Lp lacking known regulators or key enzymes for intracellular metabolism. The understanding of the metabolic strategies of different Legionella species will lead to a better understanding of fitness, virulence and persistence of legionellae and may lead to better methods for fighting these pathogens.