title: Deoxyribonucleic acid repair in a highly radiation-resistant strain of Salmonella typhimurium.
abstract: Deoxyribonucleic acid repair was studied in gamma-irradiated wild-type Salmonella typhimurium and in a radiation-resistant derivative 20 times more resistant than wild type. After exposure to 20 or 50 krad, the wild-type strain (DB21) degraded 30 to 50% of its prelabeled DNA into acid-soluble fragments, whereas the radioresistant strain degraded less than 15% after 4 h of incubation. Post-irradiation synthesis of DNA in the wild-type strain DB21 was reduced after a dose of 20 krad and totally inhibited after exposure to 200 krad. With radiation-resistant strain, D21R6008, on the other hand, DNA synthesis was delayed after a dose of 200 krad but not inhibited. Doses of 20 and 200 krad produced a similar number of single-strand breaks in the DNA of both strains as determined by zone sedimentation analysis in alkaline sucrose gradients. The radiation-resistant strain D21R6008, on the other hand, DNA synthesis was strand breaks in its DNA and repairs these damages more rapidly than wild-type Salmonella.
mesh_terms: D002247:Carbon Isotopes; D002470:Cell Survival; D002499:Centrifugation, Density Gradient; D003036:Cobalt Isotopes; D004260:DNA Repair; D004269:DNA, Bacterial / Q000096:biosynthesis* / Q000302:isolation & purification; D004277:DNA, Single-Stranded / Q000096:biosynthesis / Q000302:isolation & purification; D003839:Deoxyadenosines / Q000378:metabolism; D008970:Molecular Weight; D011830:Radiation Effects; D012486:Salmonella typhimurium / Q000378:metabolism / Q000528:radiation effects*; D013936:Thymidine / Q000378:metabolism; D013941:Thymine / Q000378:metabolism; D014316:Tritium
chemical_list: D002247:Carbon Isotopes; D003036:Cobalt Isotopes; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D003839:Deoxyadenosines; D014316:Tritium; D013941:Thymine; D013936:Thymidine