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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

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  • Mardi 10 avril 11:30-13:00 - Dr. Marianne Ilbert - « Métabolisme énergétique des bactéries extrémophiles » Bioénergétique et Ingénierie des Protéines (BIP), Marseille

    Bacterial life in acid ? Toward a better understanding of an iron respiratory chain working at pH 2

    Résumé : Microorganisms are found in various ecosystems, where they have this incredible ability to adapt to challenging conditions. Acidithiobacillus ferrooxidans, a gram negative bacterium, is the most studied and relevant model to understand how to survive in harmful environments with pH as low as pH 2 and high level of toxic metals, getting energy source from minerals containing iron and sulfur. This remarkable ability to gain energy through oxidation of ferrous iron at low pH has driven a lot of interest because of application in microbial leaching. We are currently studying the iron respiratory chain of this acidophilic organism by a multidisciplinary approach. Several metalloproteins have been identified and characterized, but the electron transfer pathway from the outer membrane to the inner membrane cytochrome c oxidase is still obscure.
    During this seminar, we will first focus our attention on the newly identified cupredoxin, AcoP, which contains a green-type copper center. We will present the crystal structure of AcoP and will discuss its spectroscopic features underlying some unexpected properties. Key residues were targeted by site directed mutagenesis to better understand the determinants driving these unusual properties. In addition, we are currently reconstituting parts of the respiratory chain with the aim to determine step by step the electron transfer pathway. The strategy is to study purified AcoP, di-heme cytochrome c and cytochrome c oxidase alone or incubated together in solution or in the immobilized state at an electrode mimicking one of the partner. Beyond thermodynamic data for each protein, this methodology offers the opportunity to decipher the molecular basis of protein-protein interaction favorable to electron transfer at low pH (A. ferrooxidans periplasmic compartment is estimated at pH 2.5). This should allow us to further describe the function of each protein in this energy chain.
    Invitée par l’équipe Adaptation bactérienne aux changements environnementaux
    Contact : Anne Durand

    Lieu : Salle Kalogeropoulos - Bâtiment 400, Campus d’Orsay

  • Mardi 5 juin 11:30-13:00 - Yoshiaki Kinosita - Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan

    Biophysical approaches to grasp the motility mechanism of microorganisms

    Résumé : The motility of organisms is driven by nano-sized molecular machines that convert chemical energy into mechanical work. The ‘conventional’ motile systems of myosin, kinesin and bacterial flagella have been studied extensively over the last several decades using various approaches such as crystal structure, gene manipulation, and functional analysis. In contrast, I have focused only on the unconventional motile system such as walking of Mycoplasma (1) and swimming archaea (2) using a single-molecular approach for 7 years. In my talk, I will show you the application of microscopic techniques to the molecular motors.
    Additionally, I will also introduce the unforeseen swimming motility of a symbiotic bacterium, Burkholderia sp. RPE64 (3). A bean bug symbiont, Burkholderia sp. RPE64, selectively colonizes the gut crypts by flagella-mediated motility : however, the mechanism for this colonization remains unclear. Remarkably, staining of the flagellar filaments with fluorescent dye Cy3 revealed that the flagellar filaments wrap around the cell body with a motion like that of a ribbon streamer in rhythmic gymnastics. Furthermore, the wrapping motion was also observed in a symbiotic bacterium of the Bobtail squid, Aliivibrio fischeri, suggesting that this motility mode may contribute to migration on the mucus-filled narrow passage connecting to the symbiotic organ.
    (1) Kinosita Y, Nakane D, Sugawa M, Masaike T, Mizutani K, Miyata M, Nishizaka T.
    Unitary step of gliding machinery in Mycoplasma mobile. Proc. Natl. Acad. Sci. USA 111, 8601-8606 (2014)
    (2) Kinosita Y., Uchida, N., Nakane, D. & Nishizaka, T. Direct observation of rotation and steps of the archaellum in the swimming halophilic archaeon Halobacterium salinarum. Nature Microbiology 1, 16148 (2016).
    (3) Kinosita Y, Kikuchi Y, Mikami N, Nakane D & Nishizaka T. Unforeseen swimming and gliding mode of an insect gut symbiont, Burkholderia sp. RPE64, with wrapping of the flagella around its cell body. ISME J 12,838-848 (2017)
    Contact : (Peter Mergaert)

    Lieu : Salle Kalogeropoulos, Bât 400, Université Paris sud - Campus Orsay

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