Stochasticité dans la réponse d'individus bactériens à une perturbation : étude dynamique

Abstract : We aim to investigate the management of the stochastic noise in gene expression and more precisely the study of noise in dynamical cellular responses. How the noise varies following a perturbation? What mechanisms are at play? How important is noise in the cellular function? To answer these questions, we are interested in the genetic regulatory network that handles the nutritional stress response in E. Coli. The noise of gene expression is quantified in a key node of the network control. For that bacteria are followed individually by fluorescence and phase contrast microscopy over several generations. This variability between cells is quantified throughout the response to the nutritional perturbation: at every moment, we know the density distribution of cellular fluorescence in the cell population. And monitoring of individual lines allows us to take into account only the population of healthy cells: individuals that do not divide neither grow, are discarded. Thereby reducing other sources of variability (e.g. cellular phenomena) we reduce the number of parameters. Noise sources are less numerous, and it is easier to understand the mechanisms at play. Also the information on cell lineage allow to study the variability introduced by the phase of the cell cycle: the events of cell division can be artificially synchronized. This study shows that the noise sounded is not dominated by differences in the phase of the cell cycle. We can therefore model our cells regardless of the differences introduced by the cell cycle. The tested model is simplified to the steps of transcription-translation-maturation. The model parameters are inferred from our experimental data and the model is tested through simulations.
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Submitted on : Wednesday, September 5, 2012 - 2:17:30 PM
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Edith Grac. Stochasticité dans la réponse d'individus bactériens à une perturbation : étude dynamique. Autre [cond-mat.other]. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENY021⟩. ⟨tel-00728293⟩

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