Molecular characterization of ilvC specialized transducing phages of Escherichia coli K-12.

Abstract

A series of lambda defective ilvC specialized transducing phage has been isolated which carry regions of isoleucine and valine structural and regulatory genes derived from the ilv cluster at minute 83 on the linkage map of the chromosome of Escherichia coli K-12. The ilv genes carried by these phages and their order have been determined by transduction of auxotrophs. The ilvC+ lysogen of an ilvC- strain gave rise, after heat induction of the lysogen, to transducing particles which carried the wild-type allele of the cya-marker. Further experiments have shown that the lambda defective ilvC phages were able to cotransduce a rho-15ts mutation as well as a rep-5 mutation. Hence, the order of the clockwise excision of the ilv cluster was found to be ilvC-rho-rep-cya. Enzyme levels in strains carrying the lambda defective ilvC phages indicated the the ilvC gene was not altered by the insertion of lambda into the ilv cluster. The isolation and digestion of lambda defective ilvC DNA by EcoRI and HindIII restriction endonucleases demonstrated that the specialized transducing phages carried part of the genome from the E. coli K-12 chromosome.