Comparison of the resA1 and polA1 Mutations in Isogenic Strains of Escherichia coli K-12

Abstract

Strains carrying either the polAl or resAl mutation are deficient in DNA polymerase I, and the polAl and resAl mutations do not complement in merozygotes. The effect of these mutations in otherwise identical genetic backgrounds was studied: after ultraviolet irradiation both strains degrade their DNA more rapidly and more extensively than the wild-type strains. However, after X-ray irradiation the resAl strain shows little DNA breakdown and repairs its single-strand breaks. In contrast, the polAl strain degrades its DNA extensively, and single-strand breaks are not repaired. Moreover, the resAl strain is capable of supporting the growth of a red-bacteriophage lambda, whereas the polAl strain is not.