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Context-dependent phenotypic switching and non-genetic memory in heterogeneous bacterial populations

Abstract : Pseudomonas fluorescens “switchers”, artificially evolved in Rainey Lab, are a model system for phenotypic switching.Populations can be characterized by the frequencies of two alternative states related tothe production of a colanic acid capsule around the cell wall. Expected to be at an equilibrium underpinned by the genetic background, such frequencies vary during population growth, hinting to a dependence of the switching rates on demography, and appear to be dependent on the history of the preculture. I thus developed a mathematical model with individual cells as bistable systems controlled by an intracellular concentration, where transition rates depend on the growth state of the population.The model quantitatively reproduces the history-dependent dynamics of the phenotypic composition of the population, and provides qualitative predictions on its quasi-steady state in exponential phase as a function of the growth rate — then corroborated by the results of my experimental work. I conclude that agrowing population of switching cells cannot be fully characterized only by the asymptotic steady state of the phenotypes’ frequencies,because phenotypic switching is inextricably intertwined with demography. From an evolutionary perspective, trans-generational inheritance of the phenotype mediated by internal concentrations may be at the basis of the emergence of bet-hedging-like strategies.
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https://tel.archives-ouvertes.fr/tel-01730121
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Submitted on : Tuesday, March 13, 2018 - 1:01:18 AM
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Orso Maria Romano. Context-dependent phenotypic switching and non-genetic memory in heterogeneous bacterial populations. Quantitative Methods [q-bio.QM]. Université Paris Saclay (COmUE), 2017. English. ⟨NNT : 2017SACLS464⟩. ⟨tel-01730121⟩

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