title: Induction of base-pair substitution and frameshift mutations in wild-type and repair-deficient strains of Salmonella typhimurium by the photodynamic action of methylene blue.
abstract: Induction of back mutations to prototrophy by methylene blue (MB)-sensitized photodynamic (PD) treatment has been studied in wild-type and repair-deficient strains of Salmonella typhimurium carrying either the base-pair substitution mutation hisG46 or the frameshift mutation hisD30529 We found that reversion of the hisG46 mutation was increased in a strain carrying a uvrB deletion and decreased in a strain carrying a recA-type mutation. Reversion of the hisD3052 (frameshift) mutation, on the other hand, was decreased in both uvrB deletion and recA-type strains. The former results are consistent with the hypothesis that the majority of MB-sensitized PD-INDUCED BASE-PAIR SUBSTITUTION MUTATIONS ARIse by a mechanism similar to that currently believed to be involved in UV mutagenesis. The latter results suggest that PD-induced frameshift mutations may arise in some other way, and two possible mechanisms involving sequential action of the excision repair and recombinational repair pathways are considered.
mesh_terms: D001483:Base Sequence; D004260:DNA Repair; D004269:DNA, Bacterial / Q000096:biosynthesis; D005815:Genetic Code; D008027:Light; D008751:Methylene Blue / Q000494:pharmacology*; D009154:Mutation; D011831:Radiation Genetics; D011995:Recombination, Genetic; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000528:radiation effects; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D008751:Methylene Blue