Hydroxyurea-sensitive mutants of bacteriophage T4

Mutagenized T4 was screened for hydroxyurea sensitivity on mutant strain Escherichia coli OK305, which was growing slowly on a synthetic medium. Most of the hydroxyurea-sensitive mutants of T4 isolated in this manner are different from those previously described by Warner et al. (1970) and Hercules et al. (1971), and several may be in new cistrons. Most of them produce fewer progeny per infected cell than wild-type T4, even in the absence of hydroxyurea. The first seven mutants studied map at seven distinct sites and affect at least five different cistrons which are scattered throughout the major early region of the T4 genetic map (between gene 38 and rI). At least one of these mutants is defective in the ability to degrade E. coli DNA.