title: Salmonella typhimurium LT2 mutation affecting the deletion of resistance determinants on R plasmids.
abstract: Plasmid Rms312, specifying resistance to tetracycline (Tc), chloramphenicol (Cm), streptomycin (Sm), sulfonamide (Su), and mercury chloride (Mer), deletes both Tc and Cm Sm Su Mer determinants at a high frequency in Salmonella typhimurium LT2. S. typhimurium mutants that were stable carriers of Rms312 were isolated by alternate culture of R-bearing cells in a medium containing either tetracycline or chloramphenicol. In one of these mutants the deletion frequency of drug resistance determinants was decreased by about 100-fold not only Rms312, but also in R100, R1, and R6-5. This mutation caused a slight reduction of ultraviolet resistance but did not affect generalized genetic recombination, indicating that the mutation is different from recA. The mutation, designated dor (deletion of r-determinants), was mapped to a position near 57 units in the new linkage map of S. typhimurijm LT2 (K. E. Sanderson and P. E. Hartman, Microbiol. Rev. 42:471-519, 1978). The dor mutation had no effect on IS1-mediated illegitimate deletion, indicating that the dor mutation is different from the del mutation described by Nevers and Saedler (P. Nevers and H. Saedler, Mol. Gen. Genet. 160:209-214, 1978).
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D005796:Genes; D009154:Mutation; D011815:R Factors; D011995:Recombination, Genetic; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents