Improving sensitivity of a small angle x-ray scattering camera with pinhole collimation using separated optical elements

International audienceWe show that a significant improvement in the sensitivity of a Huxley–Holmes design for a small angle x-ray scattering camera is obtained by separating the mirror and the monochromator. The design of the camera involves a long x-ray mirror close to a point x-ray source associated with a curved focusing crystal located close to the sample. The sample area is located at half the distance between the source and detector planes. Diffuse scattering produced by the mirror is not incident on the focusing crystal, thus reducing the background signal. Complete elimination of hard x rays allows precise calibration and hence absolute determination of sample cross section by means of a semitransparent beam stop. In pinhole geometry, the flux corresponds to a ;107 photons/s through the sample, collimated to 1022 Å21 in q range. This allows determination of scattered intensities on the order of 1023 cm21, corresponding to the scattering related to isothermal compressibility of less than 0.1 mm of pure water. As a reference sample, the widely used Lupolen™, a semicrystalline polymer, is calibrated. The high-q limit (q'4.5 nm21) of a porous calcite sample can be used as a secondary standard for specific area determination of solid/solid or solid–liquid dispersions

Fecal microbial composition associated with variation in feed efficiency in pigs depends on diet and sex

Dietary fiber content and composition affect microbial composition and activity in the gut, which in turn influence energetic contribution of fermentation products to the metabolic energy supply in pigs. This may affect feed efficiency (FE) in pigs. The present study investigated the relationship between the fecal microbial composition and FE in individual growing-finishing pigs. In addition, the effects of diet composition and sex on the fecal microbiome were studied. Fecal samples were collected of 154 grower-finisher pigs (3-way crossbreeds) the day before slaughter. Pigs were either fed a diet based on corn/soybean meal (CS) or a diet based on wheat/barley/by-products (WB). Fecal microbiome was characterized by 16S ribosomal DNA sequencing, clustered by operational taxonomic unit (OTU), and results were subjected to a discriminant approach combined with principal component analysis to discriminate diets, sexes, and FE extreme groups (10 high and 10 low FE pigs for each diet by sex-combination). Pigs on different diets and males vs. females had a very distinct fecal microbiome, needing only 2 OTU for diet (P = 0.020) and 18 OTU for sex (P = 0.040) to separate the groups. The 2 most important OTU for diet, and the most important OTU for sex, were taxonomically classified as the same bacterium. In pigs fed the CS diet, there was no significant association between FE and fecal microbiota composition based on OTU (P > 0.05), but in pigs fed the WB diet differences in FE were associated with 17 OTU in males (P = 0.018) and to 7 OTU in females (P = 0.010), with 3 OTU in common for both sexes. In conclusion, our results showed a diet and sex-dependent relationship between FE and the fecal microbial composition at slaughter weight in grower-finisher pigs

L'écosystème a-t-il une mémoire ? Importance de l'histoire sur la résilience fonctionnelle de communautés bactériennes hétérotrophes marines et anaérobies

Soutenue le 26 avril. Autre laboratoire d'accueil : Laboratoire d’Océanographie Biologique de Banyuls/mer - INSU UMR7621 CNRS Diplôme : Dr. d'UniversiteOur goal was to determine if the resilience (defined as the return to an initial state after a shock) of complex microbial communities depends on a physiological and/or structural adaptation(s) to biotic and abiotic environmental fluctuations. Using chemostats, we monitored the organic matter mineralisation simultaneously with the community structure by molecular fingerprinting techniques. We found that marine bacterial communities originating from littoral or offshore waters did not have the same functional resilience after a toluene shock. Their resiliences may depend on the physiological properties of a common culture of Alteromonas. In contrast, the environmental fluctuations select anaerobic communities. The dynamic functioning of these communities is ecologically more resilient after an acid shock. However, identical chemostats diverged over the course of incubations. The selection is, therefore, not entirely deterministic.Nous voulons déterminer si la résilience (définie comme retour à l’état initial après un choc) de consortia microbiens complexes dépend d’une adaptation physiologique et/ou structurelle aux fluctuations environnementales biotiques et abiotiques. Nous avons suivi la minéralisation de la matière organique ainsi que la structure des communautés par empreinte moléculaire dans des chemostats. Il en ressort que les consortia de bactéries marines prélevées sur le littoral ou au large n’ont pas la même résilience fonctionnelle après un choc de toluène. La résilience semble dépendre des propriétés physiologique d’une souche d’/Alteromonas/ ubiquiste. D’autre part, les fluctuations environnementales sélectionnent des communautés anaérobies. La fonction de ces communautés est écologiquement plus résiliente après un choc acide. Cependant, des chemostats identiques divergent au cours de l’incubation. La sélection n’est donc pas entièrement déterministe

Surfactin Self-Assembles into Direct and Reverse Aggregates in Equilibrium and Performs Selective Metal Cation Extraction

International audienc

Influence des conditions de logement sur la production et le stockage du scatol et de l’indole chez le porc mâle entier

Skatole and indole are involved in the problem of boar taint in entire male pigs. These molecules are produced by bacteria in the hind gut. The hygiene conditions could influence the skatole and indole levels in the fat of boars. The study was based on 115 Pietrain x (Large White x Landrace) crossbred boars, raised for 4 to 6 weeks in two contrasted hygiene conditions: a dirty and a clean room. Treatment was applied between 81±6 kg (139±1 days of age) and 117±5 kg of live weight (173±5 days of age). Pigs were dirtier in the dirty room compared with the clean one (P < 0.01). Concentrations of skatole (0.28±0.02 vs. 0.05±0.02 μg/g of liquid fat, P < 0.01) and indole (0.071±0.004 vs. 0.038±0,004 μg/g of liquid fat, P < 0.05) were higher in the dirty room. However, the hygiene conditions had no effect on the concentrations of skatole and indole in the gut contents sampled in the middle of the hindgut. Treatment effect on the volatile fatty acids composition of gut contents at the same location differed from one repetition to the next. The gut microbial composition at the same location was different for the two treatments. The difference was essentially due to bacteria belonging to the phylum Firmicutes. The relative abundance of Lactobacillus helveticus, a bacterium that produces skatole, was higher in the dirty room compared with the clean one even if the difference was significant only at four weeks of treatment. A change in gut microbiota but also an increased absorption of skatole and indole by ingestion, inhalation or through the skin could explain the higher fat concentration of both indolic compounds in the pigs maintained in the dirty environment.Le scatol et l’indole participent à l’odeur désagréable présente dans le tissu gras chez certains porcs mâles entiers. Ces molécules sont synthétisées par des bactéries dans le colon. Les conditions d’hygiène pourraient influencer leur concentration dans le gras. L’étude porte sur 115 porcs croisés Piétrain x (Large White x Landrace), élevés pendant 4 à 6 semaines dans deux conditions d’hygiène contrastées : une salle sale et une salle propre. Le traitement est appliqué entre 81±6 kg (139±1 jours d’âge) et 117±5 kg de poids vif (173±5 jours d’âge). Les animaux sont plus sales en salle sale que propre (P < 0,01). Les concentrations en scatol (0,28±0,02 vs. 0,05±0,02 μg/g de gras liquide, P < 0,01) et en indole (0,071±0,004 vs. 0,038±0,004 μg/g de gras liquide, P < 0,05) sont plus élevées en salle sale que propre. Par contre, les conditions d’hygiène n’ont pas d’effet sur les concentrations en scatol et en indole dans les contenus digestifs prélevés en milieu de colon. Les effets du traitement sur la composition en acides gras volatiles des contenus digestifs prélevés au même site diffèrent d’une répétition à l’autre. La composition du microbiote au même site diffère entre les deux traitements. Ce sont essentiellement des bactéries appartenant au phylum Firmicutes qui expliquent la différence. L’abondance relative en Lactobacillus helveticus, bactérie productrice de scatol, est plus élevée en salle sale que propre même si la différence n’est significative qu’après 4 semaines de traitement. Une modification du microbiote intestinal mais aussi une absorption accrue de scatol et d’indole par ingestion, inhalation ou via la peau pourrait expliquer l’augmentation de la concentration en composés indolés du gras des porcs élevés en salle sale

Acute challenge with a DON contaminated diet induce transient changes on microbiota composition in finishing pigs

The present study aimed at describing the impact of a deoxynivalenol (DON) - contaminated diet on microbiota composition.A total of 147 (Large White x Landrace) x Piétrain pigs from two replicates were affected to four different experimental treatments. Pigs in the control group (CC) received a control diet from 99 to 154 days of age. Groups DC, CD, and DD were given the DON-contaminated diet (3.02 mg DON/kg feed) for 7 days at 113, at 134, and at 113 and 134 days of age, respectively. The DON-contaminated diet was formulated with a naturally contaminated corn. The body weight gain and the feed intake were daily recorded from day 99 to 154. Fecal samples were collected at the beginning of the experiment (d99), immediately after the end of the 7-days DON challenges (d119 and 140), and at the end of the experiment (d154) for further 16S rRNA sequencing. During challenge periods, ADFI was decreased by 26% to 32% (P < 0.05) and ADG by 40% to 60% (P < 0.05). Short-term DON challenges induced transient changes in microbiota composition. Two weeks after the end of the DON challenges, this composition went back to control state. Whatever the age, DON challenged pigs could be discriminated from controls in a sparse PLS discriminant analysis based on 88 operational taxonomic units or 27 functional pathways with 16% error-rate. The main predictors raised by this discrimination belonged to Streptococcaceae, Lachnospiraceae and Clostridiaceae families. In our experimental conditions, changes in microbiota composition observed during DON challenges were poorly correlated to changes in ADG and ADFI. This experiment revealed a transient modification of the microbiota composition following the exposition to DON-contaminated diet, with no long-term impact on pigs’ performance

Ion Extractant as Cosurfactant at the Water-Oil Interface in Microemulsions

International audienceBicontinuous microemulsions are investigated as a model system for thespecific adsorption phenomena of metal ions at the water–oil interface. Mixingan extremely hydrophobic ion extractant – tributyl phosphate (TBP) used hereas co-surfactant- with an extremely hydrophilic sugar-based surfactant, wedescribe a new type of functionalized microemulsions that shows the classicalWinsor phases, by varying the surfactant/extractant ratio. We focus on theWinsor III-type microemulsions by determining the phase diagrams whereas themicrostructures were accessed by performing small angle neutron scatteringexperiments. Ultimately, these microemulsions may pave the way for the designof new selective ion extraction processes

L'écosystème a-t'il une mémoire ? (importance de l'histoire sur la résilience fonctionnelle de communautés bactériennes hétérotrophes marines et anaérobies)

Nous voulons déterminer si la résilience (définie comme retour à l'état initial après un choc) de consortia microbiens complexes dépend d'une adaptation physiologique et/ou structurelle aux fluctuations environnementales biotiques et abiotiques. Nous avons suivi la minéralisation de la matière organique ainsi que la structure des communautés par empreinte moléculaire dans des chemostats. Il en ressort que les consortia de bactéries marines prélevées sur le littoral ou au large n'ont pas la même résilience fonctionnelle après un choc de toluène. La résilience semble dépendre des propriétés physiologiques d'une souche d'/Alteromonas/ ubiquiste. D'autre part, les fluctuations environnementales sélectionnent des communautés anaérobies. La fonction de ces communautés est écologiquement plus résiliente après un choc acide. Cependant, des chemosats identiques divergent au cours de l'incubation. La sélection n'est donc pas entièrement déterministeLYON1-BU.Sciences (692662101) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocSudocFranceF

Liquid Interface Functionalized by an Ion Extractant: The Case of Winsor III Microemulsions

International audienceThe present work shows for the first time that tributylphosphate (TBP), the major ion extractant used in thereprocessing of spent nuclear fuel, acts efficiently as a cosurfactant in the formation of three-phase microemulsions.The system is composed of water, dodecane, TBP, and an extremely hydrophilic sugar surfactant, n-octyl-β-glucoside.The investigation of the three-phase region (Winsor III), the so-called “fish-cut” diagrams, revealed that TBP exhibitscosurfactant behavior comparable to that of classical cosurfactants n-pentanol and n-hexanol. Upon increasing thecosurfactant/surfactant molar ratio, TBP appears to be more efficient than single-chain alcohols in raising thespontaneous curvature of the adsorbed surfactant film toward oil. This is a direct consequence of the different lateralpacking of TBP and n-pentanol or n-hexanol in the mixed surfactant film, with TBP having three alkyl chains and so ahigher hydrophobic volume than those n-alcohols. This property is underlined by the interfacial film composition, whichis determined by the chemical analysis of the excess phases. It gives a surfactant to cosurfactant molar ratio of 1:1 forTBP and 1:3 for n-hexanol. Moreover, the local microstructure of the microemulsion becomes dependent on theaddition of salt when n-alcohol is replaced by TBP. A specific salt effect is also observed and rationalized in terms of thecomplexing property of TBP and Hofmeister’s effects. Treatment of the small-angle neutron scattering (SANS) datagives access to (i) the length scales characterizing the microemulsions (i.e., the persistence length, ξ, and aqueous ororganic domain sizes, D*) and (ii) the specific surface, Σ. It results that a subtle change is highlighted in the TBPmicroemulsion structure, in terms of connectivity, according to the type of salt added