The fecal microbiota of piglets during weaning transition and its association with piglet growth across various farm environments

This study describes the fecal microbiota from piglets reared in different living environments during the weaning transition, and presents the characteristics of microbiota associated with good growth of piglets after weaning. Fecal samples were collected pre- (d26) and post-weaning (d35) from 288 male piglets in 16 conventional indoor commercial farms located in the West of France. The changes one week after weaning on the most abundant microbial families was roughly the same in all farms: alpha diversity increased, the relative abundance of Bacteroidaceae (-61%), Christensenellaceae (-35%), Enterobacteriaceae (-42%), and Clostridiaceae (-32%) decreased, while the relative abundance of Prevotellaceae (+143%) and Lachnospiraceae (+21%) increased. Among all the collected samples, four enterotypes that were ubiquitous in all farms were identified. They could be discriminated by their respective relative abundances of Prevotella, Faecalibacterium, Roseburia, and Lachnospira, and likely corresponded to a gradual maturational shift from pre- to post-weaning microbiota. The rearing environment influenced the frequency of enterotypes, as well as the relative abundance of 6 families at d26 (including Christensenellaceae and Lactobacillaceae), and of 21 families at d35. In all farms, piglets showing the highest relative growth rate during the first three weeks after weaning, which were characterized as more robust, had a higher relative abundance of Bacteroidetes, a lower relative abundance of Proteobacteria, and showed a greater increase in Prevotella, Coprococcus, and Lachnospira in the post-weaning period. This study revealed the presence of ubiquitous enterotypes among the farms of this study, reflecting maturational stages of microbiota from a young suckling to an older cereal-eating profile. Despite significant variation in the microbial profile between farms, piglets whose growth after weaning was less disrupted were, those who had reached the more mature phenotype characterized by Prevotella the fastest

The multiple faces of self-assembled lipidic systems

Lipids, the building blocks of cells, common to every living organisms, have the propensity to self-assemble into well-defined structures over short and long-range spatial scales. The driving forces have their roots mainly in the hydrophobic effect and electrostatic interactions. Membranes in lamellar phase are ubiquitous in cellular compartments and can phase-separate upon mixing lipids in different liquid-crystalline states. Hexagonal phases and especially cubic phases can be synthesized and observed in vivo as well. Membrane often closes up into a vesicle whose shape is determined by the interplay of curvature, area difference elasticity and line tension energies, and can adopt the form of a sphere, a tube, a prolate, a starfish and many more. Complexes made of lipids and polyelectrolytes or inorganic materials exhibit a rich diversity of structural morphologies due to additional interactions which become increasingly hard to track without the aid of suitable computer models. From the plasma membrane of archaebacteria to gene delivery, self-assembled lipidic systems have left their mark in cell biology and nanobiotechnology; however, the underlying physics is yet to be fully unraveled

Effects of Alkaline Cations on Self-assembly of Cetylpyridinium Surfactants

International audienc

De l'image brute à l'intensité absolue : calibration d'une caméra Guinier-Méring à collimation linéaire

Nous présentons la calibration d'une caméra de type Guinier-Méring couplée à une anode au molybdène (λ=0.711 Å) et à un monochromateur de quartz. Trois jeux de fentes réduisent le faisceau à 2 mm de largeur sur 15 mm de hauteur dans le plan de l'échantillon. Une chambre à vide primaire est placée entre l'échantillon et le détecteur pour réduire l'absorption des photons diffusés par l'air. La détection se fait par des plaques photosensibles et nous utilisons le numériseur "PhosphorImager" (Molecular DynamicsTM). Pour obtenir un diagramme de diffusion où l'intensite absolue en cm-1 est tracée en fonction du vecteur d'onde q en Å-1, trois problèmes doivent être resolus : la calibration de l'axe des vecteurs d'onde ; la soustraction de la cellule vide et la calibration de l'intensite en cm-1 ; la déconvolution pour se ramener au diagramme idéal qui serait obtenu avec un faisceau ponctuel dans le plan du détecteur. La procédure peut être utilisée pour toute caméra de diffusion aux petits angles associée à des plaques photostimulables.We present here the calibration of a Guinier-Méring small angle X-ray camera. A molybdenum anode source, followed by a quartz monochromator, allows a monochromatic beam with high energy (E=17 keV, (λ=0.711 Å) to be obtained. Three set of slits limit the beam size to 2 mm width and 15 mm high at the sample position. Air scattering is reduced with a primary vacuum chamber set between the sample and the detector. An image plate is used as 2D detector. The final spectrum (absolute intensity in cm-1 plotted versus the q-vector in Å-1) requires three steps in data treatment : the calibration of the q axis, the subtraction of the empty cell and calibration of the intensity and the desmearing to make the scattering pattern what it is supposed to be with a punctual source. The method described here may be applied for any small angle X-ray camera using sensitive flat image plates

Influence of additives on the structure of surfactant-free microemulsions

We study the addition of electrolytes to surfactant-free microemulsions in the domain where polydisperse pre-Ouzo aggregates are present. As in previous studies, the microemulsion is the ternary system water/ethanol/1-octanol, where ethanol acts as co-solvent. Addition of electrolytes modifies the static X-ray and neutron scattering, and dynamic light scattering patterns, as well as the position of the miscibility gap, where spontaneous emulsification occurs upon dilution with water. All observations can be rationalized considering that electrolytes are either “salting out” the ethanol, which is the main component of the interface stabilizing the aggregates, or producing charge separation via the antagonistic ion effect discovered by Onuki et al. Amphiphilic electrolytes, such as sodium dodecylsulfate or sodium dietheylhexylphosphate, induce a gradual transition towards monodisperse ionic micelles with their characteristic broad scattering “peak”. In these micelles the ethanol plays then the role of a cosurfactant. Dynamic light scattering can only be understood by combination of fluctuations of aggregate concentration due to the vicinity of a critical point and in-out fluctuations of ethanol