Cell Division During Inhibition of Deoxyribonucleic Acid Synthesis in Escherichia coli

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Abstract
When cultures of E. coli B/r growing at various rates were exposed to UV light, mitomycin C or nalidixic acid, DNA synthesis stopped but cell division continued for at least 20 min. The chromosome configurations in the cells which divided were estimated by determining the rate of DNA synthesis during the division cycle. The cultures were pulse-labeled with l4C-thymidine, and the amount of label incorporated into cells of different ages was found by measuring the radioactivity in cells born subsequent to the labeling period. The cells which divided in the absence of DNA synthesis were those which had completed a round of chromosome replication prior to the treatments. Completion of a round of replication is probably a necessary and sufficient condition of DNA synthesis for cell division.