Geometrical structure of an iron epilayer on Si (111) : an X-ray standing wave analysis

dépôt d'une copie effectué avec l'aimable autorisation de EDP SciencesThe structure of an iron film, deposited at low temperature (50 °C) upon a silicon (111) substrate, has been determined by means of X-ray Standing Wave experiments performed at LURE (Orsay, France). Experimental results are coherent with the model of an abrupt interface between the adsorbate and the surface : the first site of adsorption terminates the bulk silicon and a body-centred iron layer epitaxially grows on the substrate with a preferential growth orientation

Méthodes alternatives in vitro pour l’étude des interactions hôte-pathogène du poumon

Les maladies respiratoires, qu’elles touchent les animaux et/ou les hommes, ont un impact sanitaire et économique considérable sur notre société. Pouvoir mieux les contrôler, les traiter et les prédire, nécessite de pouvoir les étudier. Pour cela des modèles d’études pertinents, reproductibles, efficaces aisés d’utilisation, et alternatifs à l’expérimentation animale doivent être proposés. D’énormes progrès méthodologiques ont été réalisés ces dernières années avec l’émergence de modèles in vitro qui miment le poumon en reproduisant la diversité des types cellulaires, l’architecture du tissu et certaines de ses fonctionnalités (activité ciliaire, sécrétion). Cette revue présente les avancées dans la génération de ces modèles chez le bovin : les organoïdes, les cultures Air-liquide-interface (ALI) et les coupes fines de poumon (PCLS). Ils sont utilisés pour mieux décrire et comprendre les processus physiopathologiques induits par des infections (virus, bactérie, parasite) respiratoires et permettent de tester des approches prophylactiques ou curatives

Antibiotic sensitivity reveals that wall teichoic acids mediate DNA binding during competence in Bacillus subtilis

Despite decades of investigation of genetic transformation in the model Gram-positive bacterium Bacillus subtilis, the factors responsible for exogenous DNA binding at the surface of competent cells remain to be identified. Here, we report that wall teichoic acids (WTAs), cell wall-anchored anionic glycopolymers associated to numerous critical functions in Gram-positive bacteria, are involved in this initial step of transformation. Using a combination of cell wall-targeting antibiotics and fluorescence microscopy, we show that competence-specific WTAs are produced and specifically localized in the competent cells to mediate DNA binding at the proximity of the transformation apparatus. Furthermore, we propose that TuaH, a putative glycosyl transferase induced during competence, modifies competence-induced WTAs in order to promote (directly or indirectly) DNA binding. On the basis of our results and previous knowledge in the field, we propose a model for DNA binding and transport during genetic transformation in B. subtilis

Antibiotic sensitivity reveals that wall teichoic acids mediate DNA binding during competence in Bacillus subtilis

Natural genetic transformation in bacteria requires DNA binding at the surface of competent cells. Here, Mirouze et al. show that wall teichoic acids are specifically produced or modified during competence in Bacillus subtilis and promote (directly or indirectly) DNA binding at the cell surface

MreB-dependent inhibition of cell elongation during the escape from competence in Bacillus subtilis

During bacterial exponential growth, the morphogenetic actin-like MreB proteins form membrane-associated assemblies that move processively following trajectories perpendicular to the long axis of the cell. Such MreB structures are thought to scaffold and restrict the movement of peptidoglycan synthesizing machineries, thereby coordinating sidewall elongation. In Bacillus subtilis, this function is performed by the redundant action of three MreB isoforms, namely MreB, Mbl and MreBH. mreB and mbl are highly transcribed from vegetative promoters. We have found that their expression is maximal at the end of exponential phase, and rapidly decreases to a low basal level upon entering stationary phase. However, in cells developing genetic competence, a stationary phase physiological adaptation, expression of mreB was specifically reactivated by the central competence regulator ComK. In competent cells, MreB was found in complex with several competence proteins by in vitro pull-down assays. In addition, it co-localized with the polar clusters formed by the late competence peripheral protein ComGA, in a ComGA-dependent manner. ComGA has been shown to be essential for the inhibition of cell elongation characteristic of cells escaping the competence state. We show here that the pathway controlling this elongation inhibition also involves MreB. Our findings suggest that ComGA sequesters MreB to prevent cell elongation and therefore the escape from competence

Supplementation of the maternal diet with linolenic acid (C18:3 n-3) modifies piglet gut immune system education towards LPS

Objectives and Study: N-3 polyunsaturated fatty acids (PUFA) have many beneficial health effects, especially in neonates. We recently demonstrated that supplementation of the maternal diet with alpha-linolenic acid (C18:3 n-3) increases intestinal permeability at the end of the suckling period in piglets1. Education of the gut immune system towards the colonizing microbiota, and particularly towards lipopolysaccharides (LPS) is intense during this period. We hypothesized that the increased intestinal permeability observed with maternal n-3 PUFA would lead to increased transepithelial passage of LPS and modification of the gut immune system education towards this bacterial component.Methods: Two groups of sows were fed either a flaxseed-based (n-3 group) or a sunflower oil-based diet (n-6 group) during gestation and lactation. Piglets suckled their dam until post-natal day (PND) 28 when they were weaned on a regular weaning diet. From PND 14 to 28, a sub-group of piglets in each litter received an anti-gram negative bacteria antibiotic per os daily. At PND28 and 52, FITC-labeled LPS passage across the jejunum was evaluated ex vivo in Ussing chambers. Cultures of jejunal explants were used to evaluate cytokine secretion in response to LPS. Mononuclear cells were also isolated from mesenteric lymph nodes (MLN) and cultivated with LPS or concanavalin A.Results: At PND28, passage of FITC-LPS across the jejunum was increased in n-3 piglets (P<0.05), as well as in piglets receiving the antibiotic (P<0.05). Pro-inflammatory cytokines (IL-8, TNF-α) secretion by jejunal explants was not altered by the maternal diet nor antibiotic administration. However, TNF-α secretion by MLN cells in response to LPS tended to be decreased in n-3 piglets (P=0.06) without modification of IL-10 or IFN-γ secretion. Antibiotic treatment tended to reduce this TNF-α secretion (P=0.08). Maternal diet effects were specific to LPS since no difference between groups was noticed in response to concanavalin A. Later in life (PND52), transepithelial passage of LPS was similar in both groups. TNF-α secretion by jejunal explants was reduced while IL-10 secretion by MLN cells was increased in response to LPS in n-3 piglets (P=0.01 and 0.04, respectively), irrespective of the antibiotic treatment during the suckling period.Conclusion: Supplementing the maternal diet with alpha linolenic acid during gestation and lactation orientated the gut immune system response to LPS towards an anti-inflammatory profile which lasted beyond the suckling period. This long-lasting anti-inflammatory response seems independent of microbiota composition during the suckling period

La supplémentation du régime maternel en C18 : 3n-3 modifie l'éducation du système immunitaire intestinal vis-à-vis du LPS chez le porcelet

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Influence du rapport des AGPI n-6/n-3 dans l'alimentation maternelle sur la réponse du système immunitaire intestinal du porcelet nouveau-nè au LPS bactérien

Influence du rapport des AGPI n-6/n-3 dans l'alimentation maternelle sur la réponse du système immunitaire intestinal du porcelet nouveau-nè au LPS bactérien. Congrès de la socièté de pédiatrie de l'Oues

Presence of milk phospholipids and milk lipids modified the immunomodulatory properties of infant formula in neonatal pigs

Session : Nutrition & EndoscopyPresence of milk phospholipids and milk lipids modified the immunomodulatory properties of infant formula in neonatal pigs. 4th World Congress of Pediatric Gastroenterology, Hepatology and Nutritio

Transformation efficiencies.

<p>The different <i>B</i>. <i>subtilis</i> strains studied were transformed using chromosomal DNA carrying a spectinomycin marker [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005299#pgen.1005299.ref035" target="_blank">35</a>]. Each data point has been repeated at least 5 times which provides the standard deviation presented in the second column. The last column shows the ratio between each data point and the wild-type reference.</p><p>The final Mg²⁺ concentration present in the competence medium is given in mM.</p><p>Transformation efficiencies.</p