Phase Transition Behavior in Yeast Populations Under Stress

Nonequilibrium phase transition behavior has recently been observed in computational models of evolutionary dynamics (Scott et al., 2013; King et al. 2017). Dynamical signatures predictive of population collapse have been observed in yeast populations under stress (Dai et al., 2012). We experimentally investigate the population response of Saccharomyces cerevisiae to biological stressors (temperature and salt concentration) in order to investigate the dynamical behavior of the system in the vicinity of population collapse. While both conditions lead to population decline, the dynamical characteristics of the population response differ significantly depending on the stressor. Under temperature stress, the population undergoes a sharp change with significant fluctuations within a critical temperature range, indicative of a continuous absorbing phase transition. In the case of salt stress, the response is much more gradual.