title: Dependence upon growth medium and the polA, polC, recA, recB, recC, and exrA genes of separate branches of the uvr Gene-dependent excision-repair process in Escherichia coli K12 cells.
abstract: The repair of single-strand breaks which arise in DNA during the uvr gene-dependent excision-repair process was examined in certain radiation-sensitive strains of Escherichia coli K12. The results suggest that the excision-repair process may be divided into two branches, one which is dependent on the presence of growth medium and also the rec+ exr+ genotype, and a second which can occur in buffer (growth medium independent) and is largely dependent on DNA polymerase I. DNA polymerase III appears to be involved in the growth-medium-dependent branch of excision repair, and also in the residual growth-medium-independent repair which occurs in polA1 cells. Chloramphenicol, dinitrophenol, and impurities present in some brands of agar all appear to inhibit the growth-medium-dependent branch of excision-repair. The similarities of the two branches of excision-repair to two known pathways for the repair of X-ray-induced DNA chain breaks are discussed.
mesh_terms: D002701:Chloramphenicol / Q000494:pharmacology; D003470:Culture Media; D004260:DNA Repair / Q000187:drug effects; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D005796:Genes; D008970:Molecular Weight; D011830:Radiation Effects; D011995:Recombination, Genetic; D014466:Ultraviolet Rays
chemical_list: D003470:Culture Media; D002701:Chloramphenicol