SYNCHRONIZATION OF DIVISION OF A THYMINELESS MUTANT OF ESCHERICHIA COLI

Abstract

After preliminary growth without division of E. coli strain 15T. cells in the absence of thymine in a glucose-NH4 medium, re-addition of thymine initiated active deoxyribonucleic acid (DNA) synthesis. DNA content of the cells doubled and the cells then divided synchronously while DNA synthesis stopped. Throughout the period of thymine starvation and the first division cycle in the presence of thymine the turbidity and ribonucleic acid (RNA) increased at rates similar to those observed in non-synchronized cultures. Cells synchronized in this manner divided rapidly after the division, the synchrony in the second cycle of division being less marked than that in the first or later division cycles. Synchronized cultures were infected with T2 bacteriophage in different states of the first division cycle. No significant differences were detectable in the major deter-minable parameters of the resulting one-step growth experiments as a function of the differences in division stage and stage of DNA synthesis. However cells infected in the process of DNA synthesis were more active in producing virus DNA than those infected before bacterial DNA synthesis had begun.