Half of the bacteria in the human gut microbiome are lysogens containing integrated prophages, which may activate in stressful immune environments. Although lysogens are likely to be phagocytosed by macrophages, whether prophage activation occurs or influences the outcome of bacterial infection remains unexplored. To study the dynamics of bacteria-phage interactions in living cells—in particular, the macrophage-triggered induction and lysis of dormant prophages in the phagosome—we adopted a tripartite system where murine macrophages engulf E. coli, which are lysogenic with an engineered bacteriophage λ, containing a fluorescent lysis reporter. Pre-induced prophages are capable of lysing the host bacterium and propagating infection to neighboring bacteria in the same phagosome. A non-canonical pathway, mediated by PhoP, is involved with the native λ phage induction inside phagocytosed E. coli. These findings suggest two possible mechanisms by which induced prophages may function to aid the bactericidal activity of macrophages.

人类肠道微生物组中一半的细菌是溶原菌，含有整合的原噬菌体，可以在压力很大的免疫环境中激活。尽管溶原原很可能被巨噬细胞吞噬，但是是否仍存在噬菌体激活或影响细菌感染的结果尚待探讨。为了研究活细胞中细菌-噬菌体相互作用的动力学，特别是巨噬细胞触发的吞噬体中休眠噬菌体的诱导和裂解，我们采用了三方体系，其中鼠巨噬细胞吞噬了大肠杆菌，其经工程化的噬菌体λ裂解后，含有荧光裂解报告基因。预诱导的噬菌体能够裂解宿主细菌，并传播感染到同一吞噬体中的邻近细菌。由PhoP介导的非经典途径与吞噬的大肠杆菌内部的天然λ噬菌体诱导有关。这些发现提示诱导的噬菌体可发挥作用来辅助巨噬细胞的杀菌活性的两种可能的机制。