Role of deoxyribonucleic acid polymerase III in the repair of single-strand breaks produced in Escherichia coli deoxyribonucleic acid by gamma radiation.

Cell survival, deoxyribonucleic acid (DNA) degradation, and the repair of DNA single-strand breaks were measured for Escherichia coli K-12 pol+, polA1, polC1026(ts), and polA1 polC1026(ts) cells after 137Cs gamma irradiation. The results indicate that DNA polymerase III is required for growth medium-dependent (type III) repair in polA+ or polA cells. In pol+ or polC cells, DNA polymerase I performs type II repair efficiently. The relative deficiencies of each of these strains in DNA repair generally correlate with their relative sensitivities to cell killing and with the extent of DNA degradation observed.