lexB: A New Gene Governing Radiation Sensitivity and Lysogenic Induction in Escherichia coli K12
Bacterial mutants resistant to thymine deprivation were selected from Escherichia coli K12 (λ)+. Mutants in which wild-type λ prophage had become non-inducible after thymine starvation and/or UV irradiation were isolated (Devoret and Blanco, 1970). One of them, GY6130 (Devoret et al., 1972), has a phenotype very similar to that of AB2494 lex-1 (Howard-Flanders and Boyce, 1966). It is highly sensitive to UV light and X-rays and degrades its DNA rather extensively after irradiation (see Figs. 1 and 2); furthermore, the mutant is recombination proficient and allows the growth of phage λred gam. The mutation responsible for this phenotype has been located by Hfr × F−crosses and P1 transduction; it lies near recA between cysC and pheA. Consequently, the mutation carried by GY6130 has been named IexB30; we propose that mutations mapping between malB and metA (Mount et al., 1972) be now designated lexA. Castellazzi et al. (1972) have described, in strains carrying mutation tif (Kirby et al., 1967), a mutation they called zab that suppresses the tif phenotype. Mutation IexB30 has a phenotype and a genetic location very similar to zab. We do not know yet whether or not IexB30 and zab-53 are in the same cistron. It must be pointed out that, since zab is so close to tif,it has been diffcuil to study zab out of a tif genetic background (Castellazzi, personal communication). In contrast, the study of the genotype and phenotype of lexB30 is not subject to the same limitation.
KeywordsDouble Mutant Luria Broth Bacterial Mutant Germicidal Lamp Luria Agar
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- Devoret, R., Blanco, M. and Bailone, A. (1972). Molecular Mechanisms of Genetics Processes, Nauka, Moscow, pp. 321–330.Google Scholar