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Theses

Evolution expérimentale de bactéries par brassage de génome

Abstract : This thesis focuses on experiments in bacterial evolution, with the aim to explore experimentally how horizontal transfer of DNA within a bacterial population, may or may not modify the evolution of this population. The method used to allow exchanges of DNA within the population, is based on the property of natural transformation of the bacterium Acinetobacter baylyi. A pilot experiment without genome shuffling was made over 3000 generations, and we analyzed by sequencing the mutations and the diversity that emerged during this experiment.There is a structure in multiple actively competing subpopulations that appears consistent with a system of clonal interference. An experimental evolution with exchange of DNA and a control experiment with a non- competent bacterium were performed under the same conditions over 1300 generations. The sequencing of genomes have been conducted on populations and clones at different times of each experiment to detect the mutations that occurred and their frequency in the population. Diversity in the evolution experiment with genome shuffling is significantly higher up to 970 generations and is due to different types of mutations, whereas in the control experiment diversity is mainly due to SNP. However in the experiment with shuffling, we observe a decrease in the diversity at 1300 generations which is due to the fixation of a mutation in a gene essential for transformation. These preliminary results suggest that the genome shuffling has a short term benefit while on the long term the benefit from the exchange is dwindling
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  • HAL Id : tel-00831559, version 1

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Nadia Jezequel. Evolution expérimentale de bactéries par brassage de génome. Biologie du développement. Université Pierre et Marie Curie - Paris VI, 2012. Français. ⟨NNT : 2012PAO66404⟩. ⟨tel-00831559⟩

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