Spontaneous deletion formation in several classes of Escherichia coli mutants deficient in recombination ability

Abstract

The frequency of spontaneous chromosomal deletions in 2 separate regions of the Escherichia coli chromosome has been measured in rec +. recA, recC, and rep strains. When spontaneous T7 r mutants were selected from cultures of these strains, 5–50% of the T7 r mutants were found to have become proline auxotrophs as well. Although the proportion of T7 r-Pro − deletions among T7 r mutants and the rate of T7 r formation varied according to the strain line, the state of the rec or rep alleles did not affect either of these properties within a given strain line. The rate of colB r-colV r deletion formation was also found to be independent of the state of the rec alleles and dependent upon the strain line. Thus, the products of the recA, recB, and recC loci, which are necessary for efficient recombination, and the product of the rep locus, whose function is unknown, are not required for the production of chromosomal deletions.