RésuméSelective pressure has driven evolution through the ages, forcing organisms to adapt time and again. Organisms developed strategies to face environmental stresses and maintain their fitness. In this context, Caulobacter crescentus, an oligotrophic alphaproteobacterium, has been studied to discover different systems it acquired during evolution to resist against metal stresses.
In the first part of this thesis, we characterize the Pco system of C. crescentus, providing answers about the functions and localizations of two proteins, PcoA and PcoB. We demonstrate that PcoA is a multicopper oxidase detoxifying the periplasm of C. crescentus by oxidizing copper cations. Additionally, we show that PcoB acts like an efflux pump, exporting copper ions outside the bacterium. We also investigate the role of another system, the Cus system, in the resistance against copper stresses. Finally, we conduct a large-scale in silico study, hoping to determine whether correlations exist between the conservation of genes and the behaviors, lifestyles, and environments of alphaproteobacteria.
In the second part of the thesis, we characterize an ABC transporter permease and provide data suggesting that this protein would act like a cysteine exporter. Transporting cysteine from the cytoplasm towards the periplasm could help C. crescentus resist to stresses caused by several transition metals, including copper, silver, and cadmium.
|la date de réponse||6 mars 2019|
|Sponsors||Fund for Research Training in Industry and Agriculture (FRIA)|
|Superviseur||Jean-Yves Matroule (Promoteur), Xavier De Bolle (Président), Rob Van Houdt (Jury), Jean-François Collet (Jury) & Damien Devos (Jury)|