Effects of medium pH on the yeast plasma membrane potential

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.