Thymine Metabolism in Escherichia coli

Although Escherichia coli does not readily utilize exogenous thymine for the synthesis of its deoxyribonucleic acid, cells infected with the T-even bacteriophages efficiently incorporate the exogenous base into viral DNA. The primary change induced by infection involves the entry of thymine into the cell. This alteration requires injection of the infecting viral DNA, as well as subsequent protein synthesis, but is independent of the formation of new viral DNA. It does not appear to be the result of permeability changes or of alterations in the enzymes which regulate the uptake of thymine. The results support the proposal that the uptake of exogenous thymine depends on the availability of deoxyribosyl donors for the synthesis of deoxythymidine. The altered uptake of thymine after infection probably results from a virus-induced accumulation of these deoxyribosyl donors.