UC San Diego

The phenotypic heterogeneity in homogeneous cells draws the attention of researchers since it is considered a main strategy of cells to adapt to various stresses in the environment. It is strongly related to the cellular redox status because the differences in the regulation of redox status are a known cause of this heterogeneity and because oxidative stresses are a major type of environmental threats. Previous studies have applied hydrogen peroxide to yeast cells to demonstrate the homeostatic plasticity in H2O2 stress response. In this study, a series of innovative methods were integrated to unravel the characteristics and mechanism of the phenotypic heterogeneity in homogenous yeast cells under 3 kinds of oxidative stresses. The main technique used was the combination of microfluidic platform and time-lapse microscopy, which enabled us to record the fluorescence of single yeast cells in the environment with or without oxidative stresses. The fluorescence data generated went through the process of segmentation and classification using MATLAB and Python transcripts. The application of K- Means clustering algorithm provided more insights into the distinct types of stress responses. Consequently, not only did we identify the distinct phenotypes of GFP fluorescence change in single yeast cells under different types of oxidative stresses, we also made and tested some hypotheses on the stress response mechanisms. Among the statements we made in the study, the most crucial one should be that the ability to regulate intracellular pH played an important role in the heterogeneity of stress responses. The intriguing patterns in the K-Means results were also explored with a large number of related questions to be answered in future researches.