Synthesis of Deoxyribonucleic Acid during the Division Cycle of Bacteria

Abstract

IN bacterial cultures undergoing synchronous growth, deoxyribonucleic acid has repeatedly been shown to be synthesized during part of the division cycle only (see review by Campbell, ref. 1). This could, however, be due to the physical or chemical operations used to induce synchronous division and need not reflect the normal pattern of synthesis of deoxyribonucleic acid. We have tested this possibility by examining autoradiograms of cells from uninfluenced cultures growing exponentially which had been exposed to thymidine labelled with tritium for short periods. Tritiated thymidine has already proved useful in studies of the mechanism of replication of deoxyribonucleic acid in bacteria². The present experiments indicate that during normal exponential growth, synthesis of deoxyribonucleic acid is virtually continuous.