Genetic and Physical Structures of Hybrid Bacteriophage Genomes

摘要

Escherichia coli-salmonella typhimurium hybrids provides excellent systems to isolate bacteriophage hybrids between Salmonella phage P22 and E. coli phages such as lambda, phi 80 and Mu-1. A variety of hybrid types such as lambda-P22Imlambdac, phi80immP22, amd MuimmP22 have been isolated and characterized. Studies of these hybrid phages provide invaluable information for the genetic evolution, mutation, transduction, immunity controls and gene expression of bacteriophages. We have isolated phi80immP22dis and MuimmP22dis hybrid phages carrying both c and Im regions of P22. Derivatives of phi80immP22dis which have loss the dis function were recovered from lambda80immP22dis lysogens. Such dis- derivatives were formed by replacement of a P22 phage segment containing att through Im regions with bacterial regions adjacent to prophage insertion site. Therefore the dis hybrid derivatives are high frequency transducing phages for proA, argF and metD but not for tryptophan. Although homology between phi80immP22 hybrids and P22 have been mapped in detail, phi80 segments in the hybrids have not been analyzed. Mapping of phi80 segments are now feasible since we found WR4027 amber suppressors for phi80 amber mutants.