Influence of inhibition of DNA synthesis on genetic and biochemical events in T2-infected Escherichia coli

Abstract

A specific inhibitor of the enzyme thymidylate synthetase, 5-fluorodeoxyuridine (FUDR), has been used to study Escherichia coli strain H infected with bacteriophage T2. FUDR creates a thymine deficiency and thereby depresses DNA synthesis. When the T2-infected cells are growing in minimal medium containing FUDR, the progeny phage yield is reduced to 3 infective phage per bacterium and incorporation of radiophosphorus into DNA is reduced to 10% of the normal rate; protein synthesis and RNA turnover are normal for the first 30 minutes after infection. The phage-precursor DNA pool in the inhibited cultures is 25% the size of the pool in the uninhibited cultures. More of the parental phage DNA and bacterial host DNA appears in each of the few phage produced in FUDR-treated than in the untreated cells. It seems that mature phage can be produced under conditions in which the size of the normal precursor DNA pool is greatly reduced. Genetic recombination occurs in FUDR-treated, phage-infected bacteria although the phage DNA pool is reduced and the rate of DNA synthesis is decreased. The normal (untreated) rate of recombination between unlinked or linked markers continues in FUDR until the cessation of infective phage maturation. Genetic recombination appears to be a function of time rather than of the size of the DNA pool or the rate of DNA synthesis.