Characterization of the Salmonella phage L early genes using λimm L hybrid phages

Abstract

Temperate Salmonella phage L and coliphage λ share sufficient DNA homology and similarity in genetic organization to permit construction of viable hybrid phages. Genetic and DNA heteroduplex analyses show that the λ immL hybrids retain λ head and tail genes but carry the phage L immunity locus, adjacent genes for early gene regulation, DNA replication, and (in some hybrids) general recombination. Characterization of λ immL hybrids has provided the following information about Salmonella phage L: (1) The general recombination genes of phage L resemble those of phage P22 and differ from those of phage λ with respect to Spi phenotype; (2) the immunity specificity (repressor) of phage L is different from any of the known lambdoid phage immunity types; (3) the early gene regulator (analogous to P22 gene 24 and λ gene N) is equivalent in specificity to P22 gene 24 and can suppress transcription termination in E. coli; (4) a tof activity (dependent upon gene dosage) has been inferred and is of different specificity than that expressed by phages P22 and λ; and (5) although the replication gene regions of phages L and P22 can be substituted for one another, the replication gene products are of different specificities.