Regulation of cell division in Escherichia coli.

The rate of cell division was measured in cultures of Escherichia coli B/r strain after periods of partial or complete inhibition of deoxyribonucleic acid (DNA) synthesis. The rate of DNA synthesis was temporarily decreased by removing thymidine from the growth medium or replacing it with 5-bromouracil. After restoration of DNA synthesis, a temporary period of accelerated cell division was observed. The results were consistent with the idea that chromosome replication begins when an initiator complement of fixed size accumulated in the cell. The increase in the potential for the initiation of new replication points during inhibition of DNA synthesis results in an increase in the rate of cell division after an interval which encompasses the time for the arrival of these replication points to the termini of the chromosomes and the time from this event to division.