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Martin Evans (Edinburgh)

Growth of Populations in Catastrophic Environments


(Joint work with P. Visco, R J Allen and S N Majumdar  )


Phase variation, or stochastic switching between alternative
states of gene expression, is common among microbes, and may be important
in coping with changing environments. We introduce and solve a theoretical
model for the growth of a population in an environment which produces
catastrophic events. The environment is responsive in that the rate and
distribution of catastrophe sizes depend on the state of the population.
We solve the model exactly and identify two alternative strategies which
emerge. In the “no switching” strategy, the population maximises its
instantaneous growth rate, regardless of catastrophes. In the “switching”
strategy, the switching rate is tuned to minimise the environmental