PACC1 and infection: Phage-derived antirestriction proteins, transcription, andthe replication of phage DNA are known to trigger various antiphagedefense systems, leading to bacterial abortive infection to limitviral infection and replication.50−53 Furthermore, given the “headful”DNA packaging mechanism of P1 that requires ∼100 kbp of DNAsubstrate for phage maturation,54 as wellas the ability of P1 in packaging DNA substrate without the pac sequence,55 P1 phagemid transducingparticles may be contaminated by bacterial host and/or P1 genomicDNA.