title: Comparison of the effect of nalidixic acid and thymine deprivation on excision repair in Escherichia coli.
abstract: There is a difference in the extent of inhibition of thymine dimers (TT) excision in ultravioley (UV) irradiated cells of E. coli after preirradiation depression of protein and DNA syntheses induced by a simultaneous deprivation of essential amino acids (AA-) and thymine(T-) or by deprivation of essential amino acids and addition of nalidixie acid (NAL+). This difference has been noted in both E. coli B/r Her+ and E. coli K12 SR20 uvr+ cells. Depression of DNA synthesis with the aid of malidixic acid as exogenous agent will inhibit TT excision to a lesser degree than depression of DNA synthesis by thymine starvation. The extent of TT excision has no appreciable influence on restoration of the sedimentation profile of newly synthesized DNA nor again on UV resistance of cells in conditions of dark repair. At the time when there are TT still present in DNA, the DNA molecule, having the size of the molecule of unirradiated cells, will become synthesized.
mesh_terms: D004260:DNA Repair / Q000187:drug effects; D004269:DNA, Bacterial / Q000096:biosynthesis; D004926:Escherichia coli / Q000378:metabolism* / Q000528:radiation effects; D008970:Molecular Weight; D009268:Nalidixic Acid / Q000494:pharmacology*; D011830:Radiation Effects; D013936:Thymidine / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D009268:Nalidixic Acid; D013936:Thymidine