A bacterial host factor confines phage localization for excluding the infected compartment through cell division

Viruses frequently induce the formation of specialized subcellular compartments to facilitate their replication and assembly. Here, we describe a "host-derived" confinement mechanism, compartmentalizing bacteriophage (phage) production to enable phage caging through cell division. By employing the bacterium Bacillus subtilis and its lytic phages, we identified YjbH, highly conserved among gram-positive bacteria, as a host factor that limits plaque expansion. YjbH directly binds the penetrating phage genome via its helix-turn-helix DNA-binding domain and accumulates into a focus at the site of DNA injection. YjbH further constricts the synthesis of phage components, including DNA and capsid proteins, to a specific subcellular locale. Consequently, the division machinery is recruited to produce adjacent septations, often asymmetric, effectively trapping and excluding the infected compartment. This "exclude and survive" defense mechanism may represent a prevalent strategy employed by the host to contain viral spread.