Growth of bacteriophage P1 in recombination-deficient hosts of Escherichia coli

Abstract

Growth of bacteriophage P1 was examined in normal and recombination-deficient strains of Escherichia coli. A strong correlation was found to exist between phage yields and host recombination proficiency. Measurements of burst sizes in recombination-deficient (recA) mutants, as well as in hosts mutant in the recBC, recBC, recE, or recL recombination pathways, gave values 10- to 20-fold lower than in corresponding hosts normal for recombination activity. Similarly, P1 DNA synthesis was markedly dependent on the activity of a functional recombination pathway, and in a recA mutant was equal to 5–10% of that found in the wild type host. In contrast, residual bacterial DNA synthesis in infected rec+ and recA hosts was not very different and was estimated as the equivalent of a further 0.5 and 0.3 rounds of replication, respectively, during the P1 growth cycle. Kinetic studies on P1 DNA synthesis in rec+ and recA hosts indicate two main phases of replication. An early phase of limited replication, extending up to 10–15 min after infection, was observed in both normal and mutant hosts; a second, late, phase of considerable DNA synthesis occurred only in the rec+ host. Early phage DNA synthesis was estimated as less than 0.5 rounds of replication per infecting particle and requires expression of phage-specific functions. It is concluded that host general recombination functions play an important role in phage P1 development by permitting major DNA synthesis.