Intracellular replication of choleraphage phi 92

The broad host range choleraphage phi 92 contains a linear double-stranded DNA molecule of 68 kilobase (kb) pairs with 3' overhang cohesive ends. Foll owing infection with phage phi 92, the host macromolecular synthesis is shu t off within the first 5 min, and synthesis of phage-specific DNA is detect able after 7 min of infection. At early times during infection, phage DNA i s replicated in circular form and the synthesis is membrane associated. The closed circular form serves as the precursor for the synthesis of the matu re phage DNA which is eventually packaged into the phage head. Pulse labeli ng of ultraviolet-irradiated infected cells at different times during infec tion has allowed identification of about 30 phage-specific proteins of whic h 6 are structural proteins. These proteins appear during the infection cyc le in two distinct phases, early and late. Eighteen early and 12 late prote ins have been identified.