Intracellular bacteria such as Salmonella enterica are confronted with a broad array of defence mechanisms of their mammalian host cells. The ability to sense host cell‐imposed damages, and to mount efficient stress responses are crucial for survival and proliferation of intracellular pathogens. The various combinations of host defence mechanisms acting on intracellular bacteria and their individual response also explain the occurrence of distinct subpopulations of intracellular S. enterica such as dormant or persisting, slowly or rapidly replicating cells. Here we describe a set of fluorescence protein (FP)‐based reporter strains that were used to monitor the expression of cytoplasmic or periplasmic stress response systems of single bacterial cells. This is mediated by a fast‐maturing FP as reporter for induction of stress response genes. We evaluated slower maturing FPs for a second function, that is, the analysis of the status of intracellular proliferation of pathogens. The combination of two FPs allows, at level of single bacterial cells, the interrogation of stress response and intracellular proliferation. Application of these reporters to S. enterica allowed us to detect and quantify distinct intracellular subpopulations with different levels of stress response and proliferation.

中文翻译：

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基于荧光蛋白的报告基因在单个细菌细胞水平上揭示细胞内肠沙门氏菌的应激反应

细胞内细菌，如肠道沙门氏菌，面临着其哺乳动物宿主细胞的多种防御机制。感知宿主细胞造成的损伤并产生有效的应激反应的能力对于细胞内病原体的存活和增殖至关重要。作用于细胞内细菌的宿主防御机制的各种组合及其个体反应也解释了细胞内肠球菌不同亚群的发生例如休眠或持续、缓慢或快速复制的细胞。在这里，我们描述了一组基于荧光蛋白 (FP) 的报告菌株，用于监测单个细菌细胞的细胞质或周质应激反应系统的表达。这是由快速成熟的 FP 作为报告基因介导的，用于诱导应激反应基因。我们评估了较慢成熟的 FP 的第二个功能，即病原体细胞内增殖状态的分析。两个 FP 的组合允许在单个细菌细胞水平上对应激反应和细胞内增殖进行询问。将这些记者应用于S. enterica使我们能够检测和量化具有不同压力反应和增殖水平的不同细胞内亚群。