An analysis of the processes of infection and induction of E. coli mutant hfl-l by bacteriophage lambda

The E. coli mutant hfl-1 is lysogenized with almost 100% efficiency by λ⁺ and by λcIII mutants and at a three-to fivefold increase in frequency by a λcII mutant. Elevated levels of lysogenization were also found with other lambdoid phage bearing the cIII gene of lambda (λimm⁴³⁴ and λimm²¹), but not with more distantly related lambdoid phages (λimm⁸⁰, ø80, and 424). Lytic development in the absence of repress-sor within hfl-1 and hfl⁺ strains is the same with respect to burst size and the expression of β-exonuclease, while there is within hfl-1 strains a 3–10-min delay in the time of lysis and in appearance of lysozyme. This delay in lysozyme synthesis in an hfl-1 host is dependent on the presence of the λcII gene product. Lysogens of hfl-1 strains behave normally with respect to spontaneous phage release, immunity to superinfection hy λcI, and with respect to burst size upon heat and UV induction. The latent period following UV induction of an hfl-1 strain is extended by 5–10 min. The reduced immunity of a λrim prophage is largely restored in an hfl-1 host. Nonlysogenic hfl-1 strains are abortively infected by λcl7 in the presence of functional repressor, but not in its absence. These observations suggest that the E. coli hfl-1 mutant provides an abundance of a λcIII-like product to infecting lambda phage, which, in turn, is responsible for a delay in lytic gene expression. It is this delay which enhances the establishment of repression in hfl-1 strains in the presence of normal levels of repressor.