The Gram-negative bacterium Legionella pneumophila is the causative agent of Legionnaires' disease and replicates in amoebae and macrophages within a distinct compartment, the Legionella-containing vacuole (LCV). The facultative intracellular pathogen switches between a replicative, non-virulent and a non-replicating, virulent/transmissive phase. Here, we show on a single-cell level that at late stages of infection, individual motile (P_flaA-GFP-positive) and virulent (P_ralF- and P_sidC-GFP-positive) L. pneumophila emerge in the cluster of non-growing bacteria within an LCV. Comparative proteomics of P_flaA-GFP-positive and P_flaA-GFP-negative L. pneumophila subpopulations reveals distinct proteomes with flagellar proteins or cell division proteins being preferentially produced by the former or the latter, respectively. Toward the end of an infection cycle (˜ 48 h), the P_flaA-GFP-positive L. pneumophila subpopulation emerges at the cluster periphery, predominantly escapes the LCV, and spreads from the bursting host cell. These processes are mediated by the Legionella quorum sensing (Lqs) system. Thus, quorum sensing regulates the emergence of a subpopulation of transmissive L. pneumophila at the LCV periphery, and phenotypic heterogeneity underlies the intravacuolar bi-phasic life cycle of L. pneumophila.

中文翻译：

---

群体感应控制病原体液泡外围的传播军团菌亚群

革兰氏阴性菌嗜肺军团菌是军团菌病的病原体，并在变形虫和巨噬细胞中的一个独特隔室（含军团菌的液泡 (LCV)）中复制。兼性细胞内病原体在复制、非毒力和非复制、毒力/传播阶段之间切换。在这里，我们在单细胞水平上显示，在感染的后期阶段，个体运动性（P _flaA -GFP 阳性）和毒性（P _ralF - 和 P _sidC -GFP 阳性）嗜肺军团菌出现在非感染群中。 - 在 LCV 内生长的细菌。P _flaA -GFP 阳性和 P _{flaA 的}比较蛋白质组学-GFP 阴性嗜肺军团菌亚群显示出不同的蛋白质组，鞭毛蛋白或细胞分裂蛋白分别优先由前者或后者产生。在感染周期结束时（约 48 小时），P _flaA -GFP 阳性嗜肺军团菌亚群出现在簇外围，主要逃离 LCV，并从破裂的宿主细胞扩散。这些过程由军团菌群体感应 (Lqs) 系统介导。因此，群体感应调节LCV 外围传播性嗜肺军团菌亚群的出现，而表型异质性是嗜肺军团菌液泡内双相生命周期的基础。