Abstract
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.