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Mécanismes moléculaires de l'adaptation au cours de 20 000 générations d'évolution expérimentale chez Escherichia coli.

Abstract : The molecular mechanisms of adaptation of Escherichia coli to a daily alternation between growth conditions and starvation were studied thanks to a strategy of experimental evolution. Twelve populations of E. coli, derived from a common ancestor, were propagated during more than 40,000 generations, by daily transfers in a minimal medium containing a limiting concentration of glucose. The evolution of these 12 populations is characterised by an important level of phenotypic parallelism (increase in fitness and cell volume...) as well as a genetic parallelism, the same genes being the targets of natural selection in the majority of the populations. Beneficial mutations targeting the spoT gene, involved in the stringent response allowing adaptation of bacteria to starvations, were identified in 8 populations. We highlighted beneficial mutations targeting genes involved in peptidoglycan biosynthesis (pbpA-rodA) and DNA supercoiling (topA, fis). Molecular analysis of 2 mutations in pbpA-rodA show that they induce a decrease in the concentration of the PBP2 protein. The study of 3 mutations in spoT reveals that they attenuate the stringent control during entry in stationary phase without changing cellular levels of ppGpp. Different mutations from a same gene having the same effects, evolution of the 12 populations reveals a high level of molecular parallelism. Almost half of the beneficial mutations target global regulatory networks (spoT, fis, topA). Plasticity of these networks therefore plays a crucial role during evolution and adaptation of bacteria.
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https://tel.archives-ouvertes.fr/tel-00108200
Contributor : Nadège Philippe <>
Submitted on : Thursday, October 19, 2006 - 9:22:48 PM
Last modification on : Friday, November 6, 2020 - 4:14:24 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 8:15:27 PM

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  • HAL Id : tel-00108200, version 1

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UJF | CNRS | UGA

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Nadège Philippe. Mécanismes moléculaires de l'adaptation au cours de 20 000 générations d'évolution expérimentale chez Escherichia coli.. Biochimie [q-bio.BM]. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00108200⟩

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