Bacterial mutants in which the gene N function of bacteriophage lambda is blocked have an altered RNA polymerase.

Bacterial mutants have been isolated, called groN, that block phage development by interference with the action of the product of the phage N gene. lambdatrp phages, which depend on the N product for the synthesis of tryptophan enzymes, do not make these enzymes in groN bacteria. Two type of phage mutants have been isolated that can overcome the groN block. One type makes an altered N product, the other contains an N-bypass mutation. The groN mutation is closely linked to the rifamycin-resistance locus in Escherichia coli. Purified RNA polymerase from the groN mutant is less activated by salt and more sensitive to rifamycin than is the polymerase from gro(+). This suggests that the groN mutation produces a structural change in the bacterial RNA polymerase such that it can no longer interact properly with the phage N product.