Replication of Coliphage M-13 II. Intracellular Deoxyribonucleic Acid Forms Associated with M-13 Infection of Mitomycin C-treated Cells

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Abstract
Intracellular deoxyribonucleic acid (DNA) forms associated with bacteriophage M-13 infection have been isolated and characterized. Escherichia coli HF4704 (F+, hcr−, thy−) cells were treated with mitomycin C to inhibit host-cell DNA synthesis and were then infected with phage M-13. This treatment permitted radioactive labeling of phage-specific DNA forms with 3H-thymine. These labeled DNA components were characterized by sucrose density sedimentation and equilibrium density gradient centrifugation in neutral and ethidium bromide CsCl gradient. Two double-stranded circular forms were found with properties analogous to the replicative form I and replicative form II of φX174. A third component, identified as single-stranded DNA, was isolated in some samples removed 45 min after phage synthesis was initiated.