Capacity of Extracts from Prestarved Escherichia coli to incorporate Thymidine into Deoxyribonucleic Acid

Abstract

THE ability of a polyauxotroph, Escherichia coli strain 15_T- (555–7), to synthesize deoxyribonucleic acid is temporarily lost following a period of incubation in a minimal salts–glucose medium containing thymine but no added amino-acids^1–4. Moreover, when the starved cells are returned to a medium supplemented with amino-acid, a lag in synthesis of deoxyribonucleic acid is observed^2–4. The restoration of an active deoxyribonucleic acid synthesizing system in these cells can be prevented by continued suppression of protein synthesis with chloramphenicol³ or by exposure to X-rays⁵. One possible mechanism considered was that the enzyme or enzymes involved in deoxyribonucleic acid synthesis are lost or destroyed during the starvation period and that chloramphenicol and X-ray exposure prevent resynthesis or reactivation of these components^3–5.