DNA synthesis by Escherichia coli B/r/l synchronized and grown under conditions of slow growth.

Escherichia coli B/r/l was synchronized by a novel method and its growth was followed in a minimal salts medium containing glucose, acetate, aspartate or succinate as the sole carbon source. Thymine incorporation experiments showed agreement with the Cooper-Helmstetter model for DNA synthesis, during the division cycle, both in glucose grown culture with a doubling time 57.5 min and in acetate, aspartate and succinate where the doubling time was extended up to 90 min. The ratio C/C + D was identical or close to that predicted by the model. Prolonged growth of the synchronized cultures prior to each experiment was practised in order to ensure their physiological state without causing any considerable deterioration of synchrony.