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Degradation of Cellular Deoxyribonucleic Acid After Gamma Irradiation of Spheroplasted Escherichia coli CR thy^– Cells

^a Department of Biophysics, The Pennsylvania State University, University Park, Pennsylvania 16802

ABSTRACT

Gamma-ray-irradiated Escherichia coli CR thy^– cells and spheroplasts, prelabeled with ¹⁴C-thymine, were assayed for acid-insoluble activity as a function of incubation time after irradiation. Under similar irradiation and incubation conditions, degradation profiles of cells and spheroplasts were virtually identical. Similar results were found for cells and protoplasts irradiated in the presence of rifampin (20 µg/ml). These results suggest that postirradiation deoxyribonucleic acid degradation enzymes are probably not loosely localized in the periplasm, unlike endonuclease I.

¹ Present address: The Milton S. Hershey Medical Center, Pennsylvania State University, Hershey, Pa. 17033.