Tunable bet hedging in yeast responses to osmotic stress

Microbes limit risk by stochastic bet hedging - low frequency expression of less fit, slow growing cells constitutively preadapted against many stresses including antibiotics. By contrast, here we report continuous variation in the induced frequency of cells with slow osmotic stress signaling, survival and proliferation among 50 ecologically-distinct strains of budding yeast challenged by sudden hyperosmotic stress. Despite extensive variation in early mortality, strains displayed robust perfect adaptation and recovery of steady-state viability in moderate stress. In severe stress survival depended on strain-specific proportions of cells with divergent strategies. Cautious cells survived without dividing; reckless cells attempted to divide too soon and failed, killing both mother and daughter. We show that heritable frequencies of cautious and reckless cells produce a rapidly diversifying template for microbial bet hedging that mimics natural variation in stress responses whose timing, amplitude and frequency could evolve - be tuned by - different patterns of environmental stress.