Summary
Microbes limit risk in clonal populations by stochastic bet hedging, the low frequency expression of slow growing cells constitutively resistant to the unpredictable occurrence of environmental stress including antibiotics. Also unpredictable are the severity and duration of stress. Here we describe ‘tunable’ bet hedging in 50 ecologically-distinct strains of budding yeast – continuous variation in frequencies of cells with heritable patterns osmotic stress–responsive signaling, survival and proliferation. Despite extensive variation in early mortality, after adaptation viability was perfectly restored in moderate osmotic stress. In severe stress relative fitness depended on strain–specific proportions of cells with divergent strategies. ‘Cautious’ cells survived extreme stress without dividing; ‘reckless’ cells attempted to divide too soon and failed, killing both mother and daughter. A heritable frequency of cautious and reckless cells produces a rapidly diversifying template for microbial bet hedging that resembles natural variation and is tunable by evolution in different patterns of environmental stress.