Intracellular pH changes during the cell cycle in Tetrahymena.

Area of Science:

• Cell Biology
• Biochemistry
• Physiology

Background:

• Understanding intracellular pH regulation is crucial for cell function.
• Tetrahymena pyriformis is a model organism for studying cellular processes.
• The weak acid distribution method using 5,5-dimethyloxazoladine 2,4-dione (DMO) is a common technique for estimating intracellular pH.

Purpose of the Study:

• To estimate the intracellular pH (pHi) of Tetrahymena pyriformis using the DMO distribution method.
• To investigate the relationship between external pH and pHi under normal growth conditions.
• To monitor pHi dynamics throughout the cell cycle in synchronized Tetrahymena pyriformis populations.

Main Methods:

• Utilized the equilibrium distribution of 5,5-dimethyloxazoladine 2,4-dione (DMO) to measure intracellular pH.
• Grew Tetrahymena pyriformis under controlled laboratory conditions.
• Synchronized cell populations using starvation/refeeding or heat shock methods.

Main Results:

• Intracellular pH (pHi) was maintained near 7.1 across external pH values from 5.2 to 7.3, which also represented the optimal growth range.
• DMO rapidly equilibrated across cell membranes in response to pH gradients.
• Two distinct alkaline shifts in pHi, each approximately 0.4 pH units, were observed per cell cycle, consistently correlating with the S phase of DNA synthesis.

Conclusions:

• Tetrahymena pyriformis exhibits robust intracellular pH homeostasis within an optimal growth range.
• Cell cycle progression in Tetrahymena pyriformis is associated with specific, regulated intracellular pH fluctuations.
• The observed pHi shifts are temporally linked to DNA replication and are independent of cytokinesis timing or extent.