exrB: A malB-linked gene in Escherichia coli B involved in sensitivity to radiation and filament formation

Abstract

PAM 26, a radiation-sensitive mutant of Escherichia coli strain B, is described. Its properties are attributable to a mutation in a gene, exrB, which is cotransducible with malB. It differs from uvrA (also malB-linked) derivatives of strain B in being sensitive to 1-methyl-3-nitro-1-nitroso-guanidine and γ-radiation, and in being able to reactivate UV-irradiated phage T3. It differs from exrA (also malB-linked) derivatives of strain B in forming filaments during the course of normal growth as well as after irradiation. When exrB was transduced into a K12 (lon+) strain, filaments did not form spontaneously. Three-point transductions established the order of markers as met A malB exrB. Based on an analysis of the frequency of wild-type recombinants in a reciprocal transduction between exrA and exrB strains, it was inferred that they are not isogenic and that the order of markers is malB exrA exrB. © 1974, Cambridge University Press. All rights reserved.