Manganese uptake and toxicity in magnesium-supplemented and unsupplemented Saccharomyces cerevisiae
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K J Blackwell1, J M Tobin, S V Avery
1School of Biological Sciences, Dublin City University, Ireland.
Abstract:
The magnesium content of Saccharomyces cerevisiae was found to vary by up to fivefold at differing stages of batch growth and during growth in the presence of differing magnesium concentrations. Excess Mg was primarily sequestered in vacuoles. Mn(2+)-uptake experiments revealed that Mg-enriched cells had a markedly reduced capacity for Mn2+ accumulation. For example, after 6 h incubation in the presence of 50 microM Mn2+, Mn levels were approximately twofold higher in cells previously grown in unsupplemented medium than in those from Mg-supplemented medium. These differences were further accentuated at higher Mn2+ concentrations and were not attributable to altered cell-surface charge or altered cell-surface Mn2+ binding. Cellular Mg status also influenced Mn toxicity towards S. cerevisiae. During exposure to 5 mM Mn2+, 50% reductions in the viability of cells with initial Mg contents of approximately 1400 and 2700 nmol (10(9) cells)-1 occurred after approximately 1.6 h and 3.6 h respectively. In cells containing 3300 nmol Mg (10(9) cells)-1, more than 75% viability was still maintained after 7 h incubation with 5 mM Mn2+. It is concluded that Mn2+ uptake and toxicity in S. cerevisiae are strongly influenced by intracellular Mg, possibly through Mg-dependent regulation of divalent-cation transport activity.
Insights
Magnesium (Mg) levels in yeast affect manganese (Mn) uptake and toxicity. High intracellular Mg reduces Mn accumulation and enhances yeast survival under Mn stress, suggesting Mg-dependent regulation of metal transport.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Magnesium (Mg) is an essential divalent cation for yeast growth.
- Intracellular Mg concentrations can vary significantly during yeast cultivation.
- The interaction between Mg and other essential or toxic metal ions is not fully understood.
Purpose of the Study:
- To investigate the influence of cellular magnesium content on manganese (Mn) uptake in Saccharomyces cerevisiae.
- To determine the effect of intracellular Mg status on Mn toxicity in yeast.
- To explore the potential mechanisms underlying Mg-Mn interactions in yeast.
Main Methods:
- Cultivation of Saccharomyces cerevisiae under varying Mg concentrations and growth stages.
- Measurement of intracellular Mg content and its localization (vacuolar sequestration).
- Mn(2+) uptake assays and Mn toxicity tests (viability assays) under different Mg conditions.
Main Results:
- Yeast Mg content varied up to fivefold depending on growth stage and external Mg availability.
- Mg-enriched yeast cells exhibited significantly reduced Mn(2+) uptake capacity.
- Higher intracellular Mg levels conferred increased resistance to Mn toxicity.
Conclusions:
- Intracellular magnesium status critically influences manganese uptake and toxicity in Saccharomyces cerevisiae.
- Mg-enriched cells show decreased Mn accumulation, independent of cell surface properties.
- Mg may regulate divalent cation transport, impacting Mn homeostasis and tolerance in yeast.