Phleomycin-stimulated solubilization of deoxyribonucleic acid in Escherichia coli. II. Inhibition of solubilization by bacteriophage T4.

Phleomycin-stimulated solubilization of Escherichia coli DNA is inhibited by infecting the cells with mutants of bacteriophage T4 before treatment with the antibiotic, inhibition requiring phage-specified protein synthesis. Two different modes of inhibition can be differentiated by infecting with mutants which are defective in an early state (gene den A-; endonuclease II-independent inhibition) or a late stage (gene 46-; endonuclease II-dependent inhibition) of phage-directed degradation of host DNA. Endonuclease II-independent inhibition results from interference with phleomycin-induced release of host DNA from the cytoplasmic membrane. In the presence of endonuclease II, the host DNA is converted to fragments, with average molecular weights of 10(6) daltons, the further degradation of which is not promoted by continuous exposure of the cells to phleomycin.