Intracellular Replication of Choleraphage φ92

The broad host range choleraphage φ92 contains a linear double-stranded DNA molecule of 68 kilobase (kb) pairs with 3′ overhang cohesive ends. Following infection with phage φ92, the host macromolecular synthesis is shut off within the first 5 min, and synthesis of phage-specific DNA is detectable after 7 min of infection. At early times during infection, phage DNA is replicated in circular form and the synthesis is membrane associated. The closed circular form serves as the precursor for the synthesis of the mature phage DNA which is eventually packaged into the phage head. Pulse labeling of ultraviolet-irradiated infected cells at different times during infection has allowed identification of about 30 phage-specific proteins of which 6 are structural proteins. These proteins appear during the infection cycle in two distinct phases, early and late. Eighteen early and 12 late proteins have been identified.