THE INDUCTION OF THYMINE SYNTHESIS BY T2 INFECTION OF A THYMINE REQUIRING MUTANT OF ESCHERICHIA COLI

As a result of the discovery that T2, T4, and T6 bacteriophages contained a new pyrimidine, 5-hydroxymethyl cytosine, not present in appreciable quantities in the host nucleic acids (Wyatt and Cohen, 1952), this laboratory began studies on the metabolic origin of this compound (Cohen, 1953). As one approach to this problem it seemed desirable to examine the response of pyrimidine requiring strains of Eswrichia coli to the new compound. A thymine requiring mutant of E. coli, strain 15, was obtained among others. On infection with T2 in the absence of added thymine in the medium, the infected thymineless mutant was observed to synthesize thymine, desoxyribonucleic acid (DNA), and the T2 bacteriophage. Although several instances of the induction of new metabolic capabilities by phage infection have been reported earlier in lysogenic systems (Zinder and Lederberg, 1952; Groman, 1953), this case in conjunction with the synthesis of hydroxymethyl cytosine (HMC) in T2 infected cells would appear to be the only instance of such induction in systems wherein infection leads to the inhibition of cell multiplication, and virus synthesis becomes the dominant metabolic activity.