La contamination de plusieurs poches de nutrition parentérale (PNP) par une bactérie inconnue, a déclenché une investigation, toujours en cours. Les objectifs essentiels étaient de caractériser cette bactérie sur le plan taxonomique pour permettre de la reconnaître dans d'autres contextes. Le séquençage du gène rrs, codant l'ARN 16S, a permis de positionner la bactérie inconnue parmi les Enterobacteriaceae, à proximité des genres Ewingella, Rahnella, Serratia, Yersinia et Hafnia. Le séquençage du génome total de la bactérie a permis d'utiliser cinq gènes pour une étude MLSA (multi-locus sequence analysis). L'arbre phylogénétique ainsi obtenu montre que la bactérie (six isolats ne représentant qu'une seule souche) représente un nouveau genre de la famille Enterobacteriaceae que nous avons appelé Rouxiella, l'espèce étant Rouxiella chamberiensis. Un des isolats a été désigné souche-type et déposé dans les collections dans deux pays différents (CIP, France et DSMZ, Allemagne). Les propriétés physiologiques et biochimiques de R. chamberiensis ont permis d'en faire une description. R. chamberiensis ne se développe pas à 37 °C, ce qui ne plaide pas pour une action pathogène active sur l'homme, ne produit pas de nitrate réductase (au contraire de la très grande majorité des Enterobacteriaceae, mais comme Erwinia), et ne fermente que peu de glucides. Le nom Rouxiella chamberiensis a été validé par publication dans l'International Journal of Systematic and Evolutionary Microbiology. Dès que ce nouveau genre et espèce a été publié, d'autres chercheurs ont isolé de l'environnement des souches qui étaient proches de Rouxiella. Une collaboration avec une équipe allemande a permis de décrire deux nouvelles espèces de Rouxiella, « R. badensis » et « R. sylvae » / The contamination of several parenteral nutrition bags (PNB) with unknown bacterium started an investigation, which is still ongoing. The essential objectives were: to characterize this bacterium taxonomically to allow to recognize it in others contexts. Sequencing the rrs gene (encoding 16S rRNA) allowed to position the unknown bacterium in the family Enteriobacteriaceae, close to genera Ewingella, Rahnella, Serratia, Yersinia and Hafnia. Whole genome sequencing was done. Five genes were used for a MLSA (multi-locus sequence analysis) study. The MLSA phylogenetic tree showed the bacterium (six isolates were only one strain) to represent a new genus of the family Enteriobacteriaceae, named Rouxiella, the species being Rouxiella chamberiensis. One isolate have been designated as the type strain and deposited in two collections in two different countries (CIP, France and DSMZ, Germany). The physical and biochemical properties of R. chamberiensis were used in a formal species description. R. chamberiensis failed to grow at 37 °C, this does not plead for a pathogenic action for human, negative results in tests for reduction of nitrate (which is rare in the Enterobacteriaceae, excepted Erwinia), and fermented a few carbohydrates. The name Rouxiella chamberiensis has been approved by publication in International Journal of Systematic and Evolutionary Microbiology. When this new genus and species has been published, other researchers have isolated environmental strains close to Rouxiella chamberiensis. Collaboration with a German team allowed us to describe two new species of Rouxiella, "R. badensis" and "R. sylvae"

RNA tetraloop is the smallest, simplest and the most frequent motif which is involved in numerous important biological functions. A local deviation from the RNA standard tetraloop, d2 tetraloop, has been identified with high abundance in 5S, 16S and 23S rRNAs. The presence of d2 tetraloops in highly conserved regions of 16S and 23S rRNAs suggests their functional importance. With one less residue in the loop, d2 tetraloops are considered more energetically restrained and less stable than standard tetraloops. The deletion at position j+2 in the loop is always correlated with adjacent stem distortion. MD simulations of 314-d2-tetraloop (a sample structure of d2 tetraloops) and cutd2-tetraloop (an artificially built perfect d2 tetraloop with no stem defects) have shown that stem defects are the stabilizing factor of d2 tetraloops. Simulations have also revealed that the insertion residue 318C (an example of stem defect) is stabilizing 314-d2-tetraloop by forming hydrogen bonding interactions with both the loop and the stem. When these two hydrogen bonding interactions are eliminated, the structure remained relatively stable compared to cutd2-tetraloop where the insertion residue was completely removed from the stem. This suggests the insertion residue is also stabilizing 314-d2-tetraloop by providing some conformational relaxation in the stem. Investigation of RNA standard tetraloop high temperature unfolding has revealed that the d2 tetraloop is possibly a kinetically trapped intermediate state during the folding of the standard tetraloop. High temperature unfolding simulations of standard tetraloop have shown a three-state folding behavior: a folded state, an intermediate state and an unfolded state. The folding of standard tetraloop starts with the formation of the loop. The closing base pair forms first, followed by the loop and the stem which form critical interactions such as base pairing and stacking that make a tetraloop. ROMP PNB has been investigated as supports to immobilize homogeneous catalysts to achieve both high reactivity and selectivity and easy separation. Polymers with intermediate conformational order can increase the accessibility of tethered homogeneous catalysts. Simulations of ROMP PNBDC_UD have shown the importance of bulky side groups in enabling the polymer to adopt a helical conformation. Such helical conformations have been associated with intermediate structural order in similar polymers such as PNB made by non-ROMP mechanisms. This intermediate order manifests itself as a split in the amorphous halo of WAXD pattern. Bulk simulations generated WAXD patterns that are close to the experimentally generated WAXD patterns where there are two split peaks: lower angle peak representing intermolecular interaction and higher angle peak representing intramolecular interaction.

Nanomatériaux de silice peuvent être facilement fabriqués, façonné et fonctionnalisés comme plates-formes pour le greffage des nanoparticules pour des applications biomédicales et optiques. Ici, nous utilisons une méthodologie basée sur un modèle de préparer une collection variée de hélicoïdale nanoparticules d'or (PNB) superstructures ayant impartialité contrôlable et mesures structurelles en utilisant PNB que les blocs de construction, et les nanohelices de silice que le modèle. Le matériaux présentent synthétisé bien définir Agencement chiral de PNB suivant l'hélicité de nanohelices de silice, montrant des signaux plasmoniques de dichorism circulaire (CD). D'autres observations ont prouvé ce plasmon CD vient de l'arrangement chiral de PNB et cet effet est très taille, l'échelle et dépend du pH. Nous nous attendons à ce que cette stratégie d'assemblage va découvrir une meilleure vue sur les métamatériaux et de susciter la vue vers "bottom-up" des approches en nanosciences. / Silica nanomaterials can be easily fabricated, fashioned and functionalized as platforms for grafting of nanoparticles for biomedical and optical applications. Herein, we utilize a template-based methodology to prepare a diverse collection of helical gold nanoparticle (GNPs) superstructures having controllable handedness and structural metrics by using GNPs as the building blocks, and the silica nanohelices as the template. The synthesized materials exhibit well-defined chiral arrangement of GNPs following the helicity of silica nanohelices, showing plasmonic circular dichorism (CD) signals. Further observations proved this plasmon CD comes from the chiral arrangement of GNPs and this effect is highly size, scale and pH dependent. We expect that this assembly strategy will discover a better view towards metamaterials and spark the view towards “bottom-up” approaches in nanoscience.

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