Inhibition of Bacteriophage T4 Deoxyribonucleic Acid Maturation by Actinomycin D

In the presence of 0.1 µg per ml of actinomycin D, a concentration of drug that inhibits T4 progeny formation in Escherichia coli from 98 to g 99% but does not inhibit the synthesis of macromolecules, T4-infected cells fail to synthesize mature phage deoxyribonucleic acid leading to the accumulation of a DNA species that appears to be identical with replicating T4 DNA. The data suggest that the antibiotic acts by blocking the normal packaging of phage DNA within the head membrane.