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Genomics of fitness in periodic stress

Abstract : Organisms live in dynamic environments. However, most experimental approaches study the function and selection of genes in steady environments. Therefore, natural selection acting on fluctuating environments remains poorly understood. The objective of my project was to determine if some genes are especially important for fitness (growth rate) of yeast cells in oscillating environments. A genomic screen, based on an automation of micro-cultures and on a multiplexing of sequencing libraries, allowed me to measure fitness of thousands of null mutants in periodic stress conditions. I found that predictability of fitness in periodic stress, from fitness in steady environments, varies depending on the specific genes and conditions considered. This way, some mutants have similar growth in steady conditions, and different growth in dynamic conditions. Curiously, some genes play a bivalent role: they strongly favor growth during slow fluctuations, and reduce it during fast fluctuations. I also observed many mutants with higher growth than expected at the highest frequencies of fluctuations. This effect can be partially explained by a loss of environmental sensitivity of those mutants, that continue to divide quickly despite the presence of a stress. Those results show how natural selection can act on mutations in fluctuating environments. They open the door to mechanistic studies of the predictability of fitness in periodic environments.
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Submitted on : Tuesday, October 30, 2018 - 1:02:12 AM
Last modification on : Wednesday, November 20, 2019 - 2:57:50 AM
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  • HAL Id : tel-01908203, version 1


Jérôme Salignon. Genomics of fitness in periodic stress. Molecular biology. Université de Lyon, 2017. English. ⟨NNT : 2017LYSEN055⟩. ⟨tel-01908203⟩



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