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A heat-inducible lysis-defective lambda prophage has been integrated directly into the E. coli chromosome at a site (bfe) very closely linked to the ribonucleic acid polymerase mutation rif(d), a dominant rifampin resistance allele. This unusual lysogen has facilitated the isolation of specialized transducing phages conferring rifampin resistance to sensitive cells, and carrying at least the beta subunit gene of RNA polymerase in intact form.

A temperature-sensitive mutant having a lethal mutation in the gene for the beta subunit of RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) exhibits an apparent 2- to 3-fold decrease in the rates of both beta and beta' subunit synthesis at the non-permissive temperature, relative to total protein. In contrast, a temperature-sensitive mutant with a lethal mutation in the gene encoding beta' has a 5- to 6-fold increase in the rates of beta and beta' synthesis at 42 degrees. These beta and beta' mutants also exhibit rapid degradation of both subunits at the high temperature.

A new method for isolating specialized transducing phages is described. It was used to isolate a group of phi80 transducing phages which carry various bacterial markers from the metB region of the Escherichia coli chromosome. Some of the phages selected for transduction of the supA36 marker were also shown to carry rif, a locus known to specify the beta subunit of ribonucleic acid polymerase. Expression of the prophage rif(r) gene in lysogens was demonstrated by its ability to confer rifampin resistance on part of the cellular ribonucleic acid polymerase pool.

lambdacI857s7drif(d)18 phage is a defective, specialized transducing phage carrying the RNA polymerase mutation rif(d), a dominant rifampicin-resistant allele. This phage DNA directs in vitro synthesis of the beta subunit of RNA polymerase in a DNA-dependent protein-synthesizing system. Prophage induction in cells that are lysogenic for this phage increases the rate of beta-subunit synthesis in vivo by at most 2-fold. No increase in subunit synthesis above the haploid level is observed in cells diploid for the beta gene.