Assessing yeast viability from cell size measurements?

Area of Science:

• Microbiology
• Biotechnology
• Cell Biology

Background:

• Environmental conditions significantly impact microbial cell physiology and fermentation efficiency.
• Cellular morphology, particularly cell size, changes in response to physiological alterations.
• Monitoring cell viability is crucial for optimizing microbial processes.

Purpose of the Study:

• To investigate the evolution of Saccharomyces cerevisiae cell size under various stress conditions during alcoholic fermentation.
• To assess the potential of cell size measurements as a method for inferring cell viability.

Main Methods:

• Utilized alcoholic batch fermentations with Saccharomyces cerevisiae.
• Applied stress conditions including temperature shifts, acetic acid, and furfural exposure.
• Measured cell diameter and viability using propidium iodide (PI) staining and microscopy.
• Analyzed cell size distribution using a cell counter and multivariate data analysis.

Main Results:

• Reference cultures maintained 100% viability and mean cell diameter >5µm.
• Heat stress (33°C to 43°C) at 50g/L ethanol caused growth arrest, 0% viability, and decreased mean cell diameter (5.2µm to 3.7µm).
• A subpopulation of smaller cells emerged under stress, exclusively comprising dead cells identified by PI staining.

Conclusions:

• Cell size reduction in Saccharomyces cerevisiae is a direct indicator of cell death under stress.
• Cell size distribution analysis using automated cell counters can reliably estimate dead cell ratios in fermentation processes.
• Cell size monitoring offers a valuable tool for real-time assessment of yeast health and process control.