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Updated: Jun 15, 2025
Measurement of Vacuolar and Cytosolic pH In Vivo in Yeast Cell Suspensions
Published on: April 19, 2013
Effects of medium pH on the yeast plasma membrane potential
Antonio Peña1, Norma Silvia Sánchez1, Yazmín Ramiro-Cortés2
1Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510, México City, Mexico.
Abstract:
The effects of different pH incubation values and K+ on yeast plasma membrane potential (PMP) were studied both by the fluorescence changes and the accumulation of thioflavin T (ThT), a method that has been shown most adequate for both procedures. By the changes in fluorescence of ThT, the qualitative observation of PMP at the 3 evaluated pHs indicated that cells at pH 4.0 maintain a PMP lower, but close to the observed at pH 6.0 and 7.0. By measuring the accumulation of ThT and applying the Nernst equation on the different concentrations in and out, the values of PMP could also be estimated at the different pHs, resulting in values in mV, in agreement with our observations by following the fluorescence. Yeast cells at their native niches, or during fermentations must cope with low pHs, so the importance to maintain a robust PMP to survive. The contribution of bicarbonate, derived from the fermentation to the establishment of the PMP is also described. The experiments showed once more the efficacy of the methods used with this dye.
Insights
Yeast plasma membrane potential (PMP) is maintained at low pH using thioflavin T (ThT) fluorescence. This dye effectively measures PMP, crucial for yeast survival in acidic environments like fermentation.
Area of Science:
- Biochemistry and Molecular Biology
- Microbiology
Background:
- Yeast cells must maintain plasma membrane potential (PMP) for survival, especially in acidic environments.
- Fermentation processes often expose yeast to low pH conditions.
Purpose of the Study:
- To investigate the effects of pH and potassium ions (K+) on yeast PMP.
- To evaluate thioflavin T (ThT) as a reliable dye for measuring PMP.
Main Methods:
- Utilized fluorescence changes of ThT to qualitatively assess PMP at pH 4.0, 6.0, and 7.0.
- Quantitatively measured ThT accumulation and applied the Nernst equation to estimate PMP values in mV.
- Investigated the role of bicarbonate in PMP establishment during fermentation.
Main Results:
- Cells at pH 4.0 exhibited a PMP lower than, but close to, that observed at pH 6.0 and 7.0.
- Estimated PMP values using ThT accumulation and the Nernst equation aligned with fluorescence observations.
- Demonstrated the efficacy of ThT for both qualitative and quantitative PMP assessment.
Conclusions:
- Yeast maintains a functional PMP across a range of pH values, critical for survival in acidic conditions.
- Thioflavin T is a versatile and effective dye for studying yeast plasma membrane potential.
- Bicarbonate contributes to the establishment of PMP in yeast during fermentation.
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