Emergence des nanotechnologies : Vers un nouveau "modèle industriel "?

Les technologies émergentes comme la microélectronique des années 70, les biotechnologies des années 80-90 ou les nanotechnologies des années 2000 s'expriment sous forme de vagues technologiques (Kahane, 2008) qui sont porteuses de promesses scientifiques et techniques (Pautrat, 2002), de nouveaux marchés, de perspectives de bien-être pour certains (Birraux et al., 2003), de risques, d'incertitudes et d'aliénation pour d'autres (Dupuy et al., 2004). Alors que le développement économique des nanotechnologies ne fait que commencer, plusieurs schémas de développement sont envisageables (Kahane, Mangematin, 2007).Pour plus d'informations consulter le site http://www.nanoeconomics.eu/

The Phenotypic Analysis of Lactobacillus plantarum shsp Mutants Reveals a Potential Role for hsp1 in Cryotolerance

Small heat shock proteins (sHSPs) are ubiquitous, low molecular weight (MW) proteins that share a conserved alpha-crystallin domain. sHSPs oligomers exhibit chaperon-like activities by interacting with unfolded substrates, thereby preventing their aggregation and precipitation. Unlike most lactobacilli, which have single shsp genes, three different sHSP-encoding genes, i.e., hsp1, hsp2, and hsp3, were previously identified in the probiotic Lactobacillus plantarum WCFS1. Early studies, including the characterization of the knock out (KO) mutant for hsp2, indicated a different organization and transcriptional regulation of these genes and suggested that the three L. plantarum sHSPs might accomplish different tasks in stress response. To unravel the role of sHSPs, KO mutants of hsp1 and hsp3 were generated using a Cre-lox based system. Mutation of either genes resulted in impaired growth capacity under normal conditions, heat-stress and stresses typically found during host interactions and food technological process. However, survival to heat shock and the level of thermal stabilization of cytoplasmic proteins were similar between mutants and parental strain. Transcriptional analysis revealed that in the mutant genetic backgrounds there is an upregulated basal expression of the un-mutated mate hsps and other stress-related genes, which may compensate for the loss of HSP function, hence possibly accounting for the lack of a remarkable susceptibility to heat challenge. HSP3 seemed relevant for the induction of thermotolerance, while HSP1 was required for improved cryotolerance. Cell surface properties and plasma membrane fluidity were investigated to ascertain the possible membrane association of sHSP. Intriguingly, the loss of hsp1 was associated to a lower level of maximal membrane fluidity upon heat stress. A role for HSP1 in controlling and improving membrane fluidity is suggested which may pertains its cryoprotective function

Resveratrol-Induced Xenophagy Promotes Intracellular Bacteria Clearance in Intestinal Epithelial Cells and Macrophages

Autophagy is a lysosomal degradation process that contributes to host immunity by eliminating invasive pathogens and the modulating inflammatory response. Several infectious and immune disorders are associated with autophagy defects, suggesting that stimulation of autophagy in these diseases should be beneficial. Here, we show that resveratrol is able to boost xenophagy, a selective form of autophagy that target invasive bacteria. We demonstrated that resveratrol promotes in vitro autophagy-dependent clearance of intracellular bacteria in intestinal epithelial cells and macrophages. These results were validated in vivo using infection in a transgenic GFP-LC3 zebrafish model. We also compared the ability of resveratrol derivatives, designed to improve the bioavailability of the parent molecule, to stimulate autophagy and to induce intracellular bacteria clearance. Together, our data demonstrate the ability of resveratrol to stimulate xenophagy, and thereby enhance the clearance of two invasive bacteria involved life-threatening diseases, Salmonella Typhimurium and Crohn's disease-associated Adherent-Invasive Escherichia coli. These findings encourage the further development of pro-autophagic nutrients to strengthen intestinal homeostasis in basal and infectious states

Rôle du système de communication agr dans la formation de biofilm de listeria monocytogènes : incidence sur sa persistance dans les biofilms

Diplôme : Dr. d'Universit

Rôle du système de communication AGR dans la formation de biofilm de Listeria monocytogenes (incidence sur sa persistance dans les biofilms)

Des mutants de Listeria monocytogenes possédant des délétions dans le cadre de lecture des gènes codant le régulateur transcriptionnel (agrA) et le précurseur du peptide de signalisation (agrD) ont été obtenus au laboratoire. La capacité de ces souches à se développer sous forme de biofilm sur plusieurs surfaces abiotiques a été évaluée dans différents modèles de culture de biofilm (statique et dynamique). Le nombre de cellules adhérées est affecté par la délétion de agrA et agrD quel que soit le modèle utilisé. Ces résultats suggèrent que le système agr de L. monocytogenes est impliqué dans les premières étapes de la formation de biofilm. Une nouvelle structure de biofilm composée d un réseau complexe de microcolonies reliées par des chaînettes de cellules a été mise en évidence par microscopie confocale dans le modèle de culture dynamique. L expression d agr augmente progressivement pendant la croissance du biofilm et cette expression est principalement localisée à l extérieur des microcolonies. Par ailleurs, plusieurs niveaux de régulation transcriptionnelle et post-transcriptionnelle ont été mis en évidence pour l expression d agr. La formation de biofilm de L. monocytogenes a aussi été caractérisée en présence de l espèce bactérienne Staphylococcus aureus. Une augmentation de la quantité de cellules de L. monocytogenes dans le biofilm a été observée en présence d une souche de S. aureus avec un changement de la morphologie des cellules de L. monocytogenes. Des molécules de nature peptidique présents dans le surnageant de biofilm de S. aureus semblent être impliquées dans ce phénomène, ce qui suggère que des mécanismes complexes interviennent dans cette stimulation.AgrA and agrD in frame deletion mutants of Listeria monocytogenes were constructed in the laboratory. Adhesion on abiotic surfaces (glass, polystyrene and stainless steel) and biofilm formation of these mutants were assessed under static and dynamic conditions. The number of adhered cells was affected by the deletion of agrA and agrD whatever the model used. These results suggest the involvement of the agr system of L. monocytogenes during the early stages of biofilm formation. A new structure of L. monocytogenes biofilm consisting in a network of knitted-chains was identified by confocale microscopy in a dynamic growth conditions. agr expression progressively increased during the biofilm growth and this expression was preferentially located in cells outside the knitted-chains structure. Moreover, several levels of transcriptional and post-transcriptional regulation were evidenced for agr expression. The biofilm formation of L. monocytogenes was characterized in presence of Staphylococcus aureus strains. An increase of the quantity of L. monocytogenes cells in the biofilm was noticed in the presence of one out of seven S. aureus strain with a change of the morphology of the L. monocytogenes cells. Peptide molecules within cell-free supernatants from S. aureus could be involved in this phenomenon, it suggests that complex mechanisms are involved in this stimulation.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Sensitivity to acetic acid, ability to colonize abiotic surfaces and virulence potential of Listeria monocytogenes EGD-e after incubation on parsley leaves.

International audienceAbstract Aim: To investigate how the survival of Listeria monocytogenes on parsley leaves may affect its ability to sustain process-related harsh conditions and its virulence. Methods and Results: Parsley seedlings were spot inoculated with stationary phase cells of L. monocytogenes EGD-e and incubated for 15 days. Each day, bacterial cells were harvested and enumerated, and their ability to survive acetic acid challenge (90 min, pH 4.0), to colonize abiotic surfaces and to grow as biofilms was assessed. After a 3-log decrease over the first 48 h, the population stabilized to about 10(6) CFU g(-1) until the sixth day. After the sixth day, L. monocytogenes was no longer detected, even after specific enrichment. Incubation on parsley leaves affected the ability of L. monocytogenes to survive acetic acid challenge (90 min, pH 4.0) and to adhere to stainless steel although the ability to grow as biofilm was preserved. To further investigate these physiological alterations, the mRNA levels of six target genes (bsh, clpC, groEL, inlA, opuC, prfA) was quantified using reverse transcription qPCR after 5 h of incubation on parsley leaves. A decrease was observed in all but one (bsh) target, including groEL and clpC which are involved in resistance to salt and acid. Moreover, the decrease in the levels of inlA, prfA and opuC transcripts after incubation on parsley suggested a repression of some genes involved in pathogenicity. In vitro assessment of mammalian cell adherence and invasion using Caco-2 cells confirmed the repression of the virulence factor InlA; however, the virulence potential in vivo in the chick embryo model was not affected. Conclusion: Listeria monocytogenes did undergo rapid changes to adapt its physiology to the phyllosphere. Significance and Impact of the Study: This study highlights the physiological changes undergone by L. monocytogenes during/after survival on parsley leaves

Conséquences de l'Accord Economique et Commercial Global ( AECG/CETA). Les principaux impacts de l’Accord Economique et Commercial Global (AECG/CETA) sur les productions animales européennes

International audienceNearly 10 years after the launch of the negotiations, the CETA (Comprehensive Economic and Trade Agreement) was ratified by the EU institutions in February 2017. Even though member States of the European Union (EU) still have to ratify it, the bulk of this so-called mixed" agreement (shared powers between the EU and its member states) has been applied since the provisional entry of the agreement at the end of September 2017. Indeed, the implementation of the provisions of Community competence will not wait for the final ratification of the agreement. This is particularly the case for tariff issues that will have an impact on European agriculture, in particular by reducing still significant customs duties. It also offers new opportunities for downward revision of sanitary, phytosanitary and environmental standards.A study published by the Livestock Institute, IFIP and AgroParisTech shows that this agreement could weaken European production of beef and pork, through additional imports of meat at zero customs duty at certain times.Près de 10 ans après le lancement des négociations, l’Accord Economique et Commercial Global (AECG) ou « Comprehensive Economic and Trade Agreement » (CETA, acronyme utilisé ci-après dans le texte) a été ratifié par les institutions communautaires en février 2017. Si les Etats membres de l’Union européenne (UE) doivent encore le ratifier, la majeure partie de cet accord dit « mixte » (compétences partagées entre l’UE et ses Etats membres) s’applique depuis l’entrée provisoire de l’accord fin septembre 2017. En effet, la mise en œuvre des dispositions de compétence communautaire n’attendra pas la ratification définitive de l’accord. C’est notamment le cas des questions tarifaires qui auront un impact sur les agricultures européennes, notamment par la baisse de droits de douane encore importants. Il offre également de nouvelles possibilités de révision à la baisse des normes sanitaires, phytosanitaires et environnementales. Une étude publiée par l’Institut de l’Elevage, l’IFIP et AgroParisTech montre ainsi que cet accord risque de fragiliser les productions européennes de viandebovine et porcine par des imports supplémentaires de viande à droits de douane nuls à certaines périodes