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Comparison of three forward mutation systems in Saccharomyces cerevisiae for sensitivity to polycyclic and
1SmithKline Beecham Pharmaceuticals, The Frythe, Welwyn, Herts, UK.
Abstract:
Forward mutation to cycloheximide resistance, L-canavanine resistance and DL-alpha-aminoadipic acid resistance in Saccharomyces cerevisiae wild-type strain S7a was tested for sensitivity to nine mutagens in treat-and-plate assays. Eight of these agents, 2-aminofluorene, 2-acetylaminofluorene, benzo[a]pyrene, benzidine, cyclophosphamide, acriflavine, 7,12-dimethylbenz[a]anthracene and 2-aminoanthracene were known or suspected to be difficult to detect whilst one, methyl methanesulphonate, was known to be very active in yeast. Forward mutation to cycloheximide resistance was, overall, the most sensitive system, detecting all nine agents under optimal conditions, although neither benzidine nor benzo[a]pyrene were consistently positive. Mutation to adipic acid resistance occasionally gave responses superior to those at the cycloheximide loci, but mutation to canavanine resistance was never more sensitive than the cycloheximide resistance system. We conclude that forward mutation in strain S7a using both cycloheximide and adipic acid resistance loci is capable of detecting the genetic effects of a range of polycyclic and heterocyclic compounds with greater sensitivity than is seen in other published gene mutation assays with yeast. Although sensitivity is much lower than in bacterial assays, such yeast assays provide a reasonable alternative to bacterial genotoxicity screening for agents such as potent bactericides.
Insights
Forward mutation assays in Saccharomyces cerevisiae using cycloheximide resistance are highly sensitive for detecting genotoxic agents. This yeast assay offers a viable alternative to bacterial screening for potent bactericides.
Area of Science:
- * Molecular Biology
- * Genetics
- * Toxicology
Background:
- * Assessing the genotoxicity of various chemical compounds is crucial for public health and environmental safety.
- * Traditional bacterial mutagenicity assays may not be suitable for all compounds, especially potent bactericides.
- * Yeast-based assays offer an alternative model system for genotoxicity testing.
Purpose of the Study:
- * To evaluate the sensitivity of different forward mutation systems in Saccharomyces cerevisiae for detecting genotoxic agents.
- * To compare the efficacy of yeast assays against bacterial assays for genotoxicity screening.
Main Methods:
- * Forward mutation assays were conducted in Saccharomyces cerevisiae wild-type strain S7a.
- * Tested resistance to cycloheximide, L-canavanine, and DL-alpha-aminoadipic acid.
- * Evaluated sensitivity to nine mutagens, including polycyclic and heterocyclic compounds, using treat-and-plate assays.
Main Results:
- * The cycloheximide resistance system demonstrated the highest sensitivity, detecting all nine tested mutagens under optimal conditions.
- * Mutation to adipic acid resistance occasionally showed superior responses compared to cycloheximide resistance.
- * L-canavanine resistance was consistently less sensitive than the cycloheximide resistance system.
Conclusions:
- * Forward mutation assays in yeast strain S7a, particularly using cycloheximide and adipic acid resistance, effectively detect genetic effects of various compounds.
- * These yeast assays provide greater sensitivity for certain compounds than previously published yeast gene mutation assays.
- * Yeast genotoxicity assays serve as a practical alternative to bacterial screening for agents like potent bactericides.