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Département Microbiologie

Séminaires Microbiologie

Les événements Microbiologie sont affichés en bleu dans l’agenda I2BC...

La prochaine journée du département aura lieu le 28 avril 2017.
Contact : Nathalie Dautin

publié le , mis à jour le


  • Mardi 3 octobre 11:30-12:30 - Dr Alexandre Chenal - Groupe BiophysiCyaA Laboratoire de Biochimie des Intéractions Macromoléculaires Département de Biologie Structurale et Chimie Institut Pasteur, Paris

    La toxine CyaA de Bordetella pertussis : de la biogénèse à la piraterie

    Résumé : The adenylate cyclase toxin (CyaA, 1706 residues) is an RTX protein that plays an essential role in the early stages of respiratory tract colonization by Bordetella pertussis, the causative agent of whooping cough. Its cell intoxication process, however, is still poorly understood. After its secretion through a dedicated type 1 secretion system, CyaA intoxicates human cells via a unique mechanism of translocation of its catalytic domain (AC) directly across the plasma membrane of target cells. Once in the cytosol, AC interacts with calmodulin (CaM) and produces supraphysiological levels of cAMP, leading to cell death. I will present some recent data, which covers several steps of this intoxication process. Our results illustrate the structural flexibility of bacterial toxins adapted to various functions and contexts, such as toxin secretion and refolding, AC translocation, and enzymatic AC:CaM complex formation. Our data further shows the adaptation of bacterial RTX toxins to the diverse array of calcium concentrations encountered in the successive environments during the intoxication process. Finally, due to its hydrophobic character, CyaA is known for its propensity to aggregate into multimeric forms in the absence of a chaotropic agent in vitro. We have recently defined the experimental conditions required for CyaA folding into a stable, monomeric and functional form. This opens new perspectives for both basic science and CyaA-based biotechnological applications developed in the lab, i.e., to improve antigen delivery vehicles and new pertussis vaccines.

    Lieu : Salle A. Kalogeropoulos - Bâtiment 400, campus d’Orsay

  • Mardi 14 novembre 11:30-12:30 - Dr George Di Cenzo - Department of Biology, University of Florence, Florence, Italy

    Experimental and in silico guided approaches to studying the rhizobium-legume symbiosis

    Résumé : Rhizobia are bacterial species capable of fixing atmospheric nitrogen gas to ammonium in symbiosis with a plant host, an agriculturally and ecologically important process. Our group studies Sinorhizobium meliloti as a model rhizobium, using both experimental genetic and in silico approaches. In this talk, I will describe our efforts aimed at identifying the S. meliloti gene set that is both necessary and sufficient for symbiotic nitrogen fixation, which is based upon a large-scale genome manipulation strategy involving the deletion of nearly 3,000 genes. Two specific stories arising from this work will be described to highlight the potential of this approach in advancing our understanding of the genetics of symbiosis. I will also describe our work in reconstructing an in silico genome-scale S. meliloti metabolic network, and how we are using this metabolic model with flux balance analysis to study the genetics and metabolism of S. meliloti as a free-living organism and during symbiosis with a host plant.
    Invité par l’Equipe "Intéractions Plantes-Bactéries"

    Lieu : Salle A. Kalogeropoulos - Bâtiment 400, campus d’Orsay

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