Interference of aging media on the assessment of yeast chronological life span by propidium iodide staining

An increasing number of researchers are using the Saccharomyces cerevisiae chronological aging model to gain insight into the post-mitotic cellular aging. Recently, an alternative approach to the traditional cellular viability assay by colony-forming unit (CFU) counts, based on the propidium iodide (PI) staining combined with flow cytometry (PI-FCM), was proposed for the assessment of yeast chronological aging. Since the chronological aging assessment shows variations particularly concerning the aging media, in this work, the influence of the most common aging media (exhausted media or water) on the assessment of chronological aging by PI staining was studied. Our results show that this methodology is highly affected by the aging media. Indeed, a correlation between CFU counts and the percentage of PI-stained cells is only achieved with the exhausted media. As such, the assessment of yeast chronological aging by PI-FCM water should not be used.