Experimental evolution with bacteria

Orateur : Thomas HINDRE (LAPM, CNRS UMR 5163 – UJF, Grenoble)

Epistatic interactions are major contributo rs to fundamental evolutionary processes. During the longest-running evolution experiment, we previously demonstrated that E.coli populations evolved through unknown changes in epistatic interactions between major hubs within the regulatory network, causing a large expansion of the regulon controlled by the master regulator CRP. We investigated the evolutionary dynamics of this expansion together with the molecular mechanism underlying the rewiring of the crp transcriptional network. Growth and global transcription profiles over evolutionary time allowed us to show that this rewiring occurred early during evolution. A single point mutation was specifically responsible for the expansion of the CRP regulon. Different alleles of one unique hub gene therefore imposed profoundly altered architechture of E.coli regulatory networks. These data document regulatory networks evolvability and the contribution of epistatic interactions to bacterial adaptation.

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