Antimutagenesis in yeast by sodium chloride, potassium chloride, and sodium saccharin
1Department of Genetics, University of Alberta, Edmonton, Canada.
Abstract:
Aqueous salt solutions containing NaCl, KCl, MgCl2, Na2SO4, CaCl2, NH4Cl, or sodium saccharin are mutagenic in yeast when logarithmic growth of cells is interrupted by exposure to a 0.5-2.0 M salt solution. Stationary-phase cells are not mutated by this treatment. When placed in an enriched medium with the salt, the stationary-phase cells grow after a prolonged lag period. The compounds tested (NaCl, KCl, and sodium saccharin), under conditions in which growth in medium can take place, exhibit an antimutagenic response as measured by the compartmentalization test. The antimutagenic action of salt solutions in yeast is concentration-dependent. Unlike the mutagenic action of these compounds, which approximates an osmolality-dependent response, the antimutagenic action seems to be correlated with toxicity as measured by growth rate reduction at increasing concentrations of the compounds. For example, sodium saccharin and NaCl exhibit almost identical osmolalities; however, 0.3 M sodium saccharin reduces the growth rate much more than does 0.3 M NaCl. At these same molar concentrations, the spontaneous mutation rate for histidine prototrophy is, for the control, 6.2 x 10(-8) mutations/cell/-generation, 3.5 x 10(-8) with 0.3 M NaCl, and 1.7 x 10(-8) with 0.3 M sodium saccharin.
Insights
Aqueous salt solutions can be mutagenic to yeast cells during logarithmic growth but not in stationary phase. These salts also show antimutagenic properties, with effects depending on concentration and toxicity.
Area of Science:
- * Molecular and Cellular Biology
- * Genetics and Genomics
- * Yeast Genetics and Mutagenesis
Background:
- * Aqueous salt solutions are common in biological systems and industrial processes.
- * Understanding their effects on cellular processes, including mutagenesis, is crucial.
- * Previous research has indicated potential genotoxic effects of various compounds.
Purpose of the Study:
- * To investigate the mutagenic and antimutagenic effects of aqueous salt solutions in yeast.
- * To determine the influence of cell growth phase (logarithmic vs. stationary) on salt-induced mutagenesis.
- * To explore the relationship between salt concentration, osmolality, toxicity, and their impact on mutation rates.
Main Methods:
- * Yeast (Saccharomyces cerevisiae) cultures were exposed to various salt solutions (NaCl, KCl, MgCl2, Na2SO4, CaCl2, NH4Cl, sodium saccharin) at different concentrations (0.5-2.0 M).
- * Mutagenesis was assessed in both logarithmic and stationary growth phases.
- * Antimutagenic effects were evaluated using the compartmentalization test, measuring spontaneous mutation rates for histidine prototrophy under varying salt concentrations and correlating with growth rate reduction.
Main Results:
- * Aqueous salt solutions were mutagenic to yeast in the logarithmic growth phase but not in the stationary phase.
- * Stationary-phase cells exhibited a prolonged lag period before growth resumption in the presence of salts.
- * Tested compounds (NaCl, KCl, sodium saccharin) demonstrated an antimutagenic response in growth conditions, with effects being concentration-dependent and correlated with toxicity (growth rate reduction), not solely osmolality.
Conclusions:
- * The mutagenicity of aqueous salt solutions in yeast is dependent on the cell's growth phase.
- * These salts exhibit a dual role, acting as mutagens under specific conditions and antimutagens under others.
- * Antimutagenic activity is linked to cellular toxicity, suggesting a complex interplay between salt concentration, cell physiology, and genetic stability.
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