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Accueil > Plateformes > Plateformes IMAGERIE-GIF : Cytométrie, Microscopie Electronique & Microscopie Photonique > Publications & Communications

Microscopie Electronique

2018


  • M. Blondeau, M. Sachse, C. Boulogne, C. Gillet, J. - M. Guigner, F. Skouri-Panet, M. Poinsot, C. Ferard, J. Miot, et K. Benzerara, « Amorphous Calcium Carbonate Granules Form Within an Intracellular Compartment in Calcifying Cyanobacteria », Frontiers in Microbiology, vol. 9, p. 1768, 2018.
    Résumé : The recent discovery of cyanobacteria forming intracellular amorphous calcium carbonate (ACC) has challenged the former paradigm suggesting that cyanobacteria-mediated carbonatogenesis was exclusively extracellular. Yet, the mechanisms of intracellular biomineralization in cyanobacteria and in particular whether this takes place within an intracellular microcompartment, remain poorly understood. Here, we analyzed six cyanobacterial strains forming intracellular ACC by transmission electron microscopy. We tested two different approaches to preserve as well as possible the intracellular ACC inclusions: (i) freeze-substitution followed by epoxy embedding and room-temperature ultramicrotomy and (ii) high-pressure freezing followed by cryo-ultramicrotomy, usually referred to as cryo-electron microscopy of vitreous sections (CEMOVIS). We observed that the first method preserved ACC well in 500-nm-thick sections but not in 70-nm-thick sections. However, cell ultrastructures were difficult to clearly observe in the 500-nm-thick sections. In contrast, CEMOVIS provided a high preservation quality of bacterial ultrastructures, including the intracellular ACC inclusions in 50-nm-thick sections. ACC inclusions displayed different textures, suggesting varying brittleness, possibly resulting from different hydration levels. Moreover, an electron dense envelope of ∼2.5 nm was systematically observed around ACC granules in all studied cyanobacterial strains. This envelope may be composed of a protein shell or a lipid monolayer, but not a lipid bilayer as usually observed in other bacteria forming intracellular minerals. Overall, this study evidenced that ACC inclusions formed and were stabilized within a previously unidentified bacterial microcompartment in some species of cyanobacteria.
    Mots-clés : amorphous calcium carbonate, bacterial microcompartment, biomineralization, ca, calcification, carboxysome, CEMOVIS, MET, PF.

2017



  • J. Marion, R. Le Bars, B. Satiat-Jeunemaitre, et C. Boulogne, « Optimizing CLEM protocols for plants cells: GMA embedding and cryosections as alternatives for preservation of GFP fluorescence in Arabidopsis roots », Journal of Structural Biology, 2017.
    Mots-clés : Arabidopsis, BIOCELL, Correlative microscopy, DYNBSJ, GFP, GMA resin, IMAGIF, MET, PF, PHOT, Tokuyasu, Transmission electron microscopy.

  • Y. Wu, V. Pons, A. Goudet, L. Panigai, A. Fischer, J. - A. Herweg, S. Kali, R. A. Davey, J. Laporte, C. Bouclier, R. Yousfi, C. Aubenque, G. Merer, E. Gobbo, R. Lopez, C. Gillet, S. Cojean, M. R. Popoff, P. Clayette, R. Le Grand, C. Boulogne, N. Tordo, E. Lemichez, P. M. Loiseau, T. Rudel, D. Sauvaire, J. - C. Cintrat, D. Gillet, et J. Barbier, « ABMA, a small molecule that inhibits intracellular toxins and pathogens by interfering with late endosomal compartments », Scientific Reports, vol. 7, nᵒ 1, p. 15567, nov. 2017.
    Résumé : Intracellular pathogenic microorganisms and toxins exploit host cell mechanisms to enter, exert their deleterious effects as well as hijack host nutrition for their development. A potential approach to treat multiple pathogen infections and that should not induce drug resistance is the use of small molecules that target host components. We identified the compound 1-adamantyl (5-bromo-2-methoxybenzyl) amine (ABMA) from a cell-based high throughput screening for its capacity to protect human cells and mice against ricin toxin without toxicity. This compound efficiently protects cells against various toxins and pathogens including viruses, intracellular bacteria and parasite. ABMA provokes Rab7-positive late endosomal compartment accumulation in mammalian cells without affecting other organelles (early endosomes, lysosomes, the Golgi apparatus, the endoplasmic reticulum or the nucleus). As the mechanism of action of ABMA is restricted to host-endosomal compartments, it reduces cell infection by pathogens that depend on this pathway to invade cells. ABMA may represent a novel class of broad-spectrum compounds with therapeutic potential against diverse severe infectious diseases.
    Mots-clés : MET, PF.
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par Marion Blin - publié le , mis à jour le