Studies with a λrif Transducing Phage Carrying the Genes for the β and β′ Subunits of E. coli RNA Polymerase

Abstract

INTRODUCTION
Specialized transducing phages carrying specific bacterial genes or sets of genes have contributed greatly to our understanding of bacterial systems at both the genetic and the biochemical level. To facilitate the genetic analysis of Escherichia coli RNA polymerase (E.C. 2.7.7.6) and to provide a means for ultimately studying in vitro the regulation of the synthesis of the various polymerase subunits, λ transducing phages were isolated (Kirschbaum 1973a; Kirschbaum and Konrad 1973) that were initially shown to carry the gene for the β subunit (Kirschbaum 1973b). Subsequent genetic studies established that many of these transducing phages carried the structural gene for the β′ subunit as well (Kirschbaum and Scaife 1974). This observation is consistent with the recent finding that the genes encoding the β and β′ subunits are organized in the form of a single operon on the bacterial chromosome (Errington et al. 1974).

The direct selection of phages carrying at least the β subunit gene (rif) was made possible by the isolation of a dominant rifampicin resistance mutation, rif^d (Kirschbaum 1973a). This series of rif^d transducing phages was generated by heat induction of an unusual λ lysogen in which λC1857S7 had been integrated into a site (bfe) on the bacterial chromosome that was very closely linked to rif (Figure 1) in a strain carrying the rif^d mutation (Kirschbaum 1973a; Kirschbaum and Konrad 1973).

This report is the result of several independent studies involving one such phage, λc1857S7drif^d18 (hereafter referred to as λdrif^d18), and describes (a) the determination of the...