title: Isolation of "relaxed" mutants of Escherichia coli.
mesh_terms: D002247:Carbon Isotopes; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects; D005827:Genetics, Microbial; D009154:Mutation; D010406:Penicillins / Q000494:pharmacology; D012329:RNA, Bacterial / Q000096:biosynthesis; D014161:Transduction, Genetic; D014466:Ultraviolet Rays; D014498:Uracil / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D010406:Penicillins; D012329:RNA, Bacterial; D014498:Uracil