Dr. Ingo Lohmar

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It is now well-established that individual bacteria of many types switch
stochastically between two phenotypes: fast-growing "normals"
susceptible to antibiotics, and slowly-growing "persisters" hardly
affected by the drug. In the competition of species during exponential
growth, persisters are a burden, but they may become beneficial when
introducing "stress" phases like drug treatment.
We suggest to shift the focus to the persistence of an
established population. Due to fluctuations, the population will (after
a long time) eventually go extinct; persisters act as a life insurance
against this. We study a simple stochastic model of these processes.
Using a WKB approximation, we find the most likely path to extinction
and quantify the extinction risk under both favorable and adverse
conditions. Analytical results are obtained both in the biologically
relevant regime when the switching is rare compared with the birth and
death processes, and in the opposite regime of frequent switching. We
explain how persisters strongly reduce the extinction risk and show that
rare switches are most beneficial to this end.

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Racah Institute of Physics, Jerusalem
Konferenzraum des Instituts für Theoretische Physik
Contact: not specified