Isolation and characterization of λdargECBH transducing phages and heteroduplex analysis of the argECBH cluster

Abstract

Transducing λ bacteriophages have been isolated which carry the divergently transcribed argECBH operon of E. coli K12 and various portions of the adjacent ppc and bfe chromosomal regions. They were recovered from lysates prepared by the procedure of Schrenk and Weisberg using a Ppc⁺ Arg⁺ Bfe⁺ strain carrying a deletion of the usual attachment site of λ. Heteroduplex DNA mapping of these λdarg and of the ϕ80 darg isolated by B. Konrad indicates that the two kinds of phages carry the arg cluster in opposite orientations, a situation favorable for the isolation of argECBH DNA. A physical map of the ppc argECBH bfe region including 2 unusual attachment sites of λ has been constructed. The localization of the end points of certain arg deletions provides a useful reference framework for the currently pursued mapping of mutations affecting the control of divergent transcription and for the location of restriction enzyme cleavage sites in the arg region.