Development of a Detailed Microphysics Cirrus Model Tracking Aerosol Particles' Histories for Interpretation of the Recent INCA Campaign

International audienceCirrus clouds play an important role in the earth's energy balance. To quantify their impact, information is needed on their microstructure and more precisely on the number and size of the ice crystals. With the anthropogenic activity, more and more aerosol particles and water vapor are released even at the altitude where cirrus clouds are formed. Cirrus clouds formed in a polluted air mass may have different microphysical properties and, therefore, a different impact on the climate system via the changed radiative properties compared to background cirrus clouds. To study this aspect, the European project called the Interhemispheric Differences in Cirrus Properties due to Anthropogenic Emissions (INCA) measured the microphysical properties of cirrus clouds together with the physical and chemicals properties of aerosol particles in clean air (at Punta Arenas, Chile) and polluted air (at Prestwick, Scotland). The goal of the present work was to develop a detailed microphysics model for cirrus clouds for the interpretation and the generalization of the INCA observations. This model considers moist aerosol particles through the Externally Mixed (EXMIX) model, so that the chemical composition of solution droplets can be followed. Ice crystal formation is described through homogeneous or heterogeneous nucleation. The crystals then grow by deposition. With this model, the interactions between the microphysical processes, simulated ice crystal concentrations, and dimensional distributions of the INCA observations were studied, and explanations were provided for the observed differences between background and polluted cirrus clouds

Polarized light scattering by inhomogeneous hexagonal monocrystals. Validation with ADEOS-POLDER measurements

Various in situ measurements of the light-scattering diagram in ice clouds were performed with a new nephelometer during several airborne campaigns. These measurements were favorably compared with a theoretical scattering model called Inhomogeneous Hexagonal Monocrystal (IHM) model. This model consists in computing the scattering of light by an ensemble of randomly oriented hexagonal ice crystals containing spherical impurities of soot and air bubbles. It is achieved by using a combination of ray tracing, Mie theory, and Monte Carlo techniques and enables to retrieve the six independent elements of the scattering matrix. This good agreement between nephelometer measurements and IHM model provides an opportunity to use this model in order to analyze ADEOS-POLDER total and polarized reflectance measurements over ice clouds. POLDER uses an original concept to observe ice cloud properties, enabling to measure reflectances and polarized reflectances, for a given scene, under several (up to 14) viewing directions. A first analysis of ice cloud spherical albedoes over the terrestrial globe for November 10, 1996, and April 23, 1997, shows a rather good agreement between measurements and modeling. Moreover, polarized reflectances are also calculated and show a satisfactory agreement with measurements

Microbial Communities of the Shallow-Water Hydrothermal Vent Near Naples, Italy, and Chemosynthetic Symbionts Associated With a Free-Living Marine Nematode

Shallow-water hydrothermal vents are widespread, especially in the Mediterranean Sea, owing to the active volcanism of the area. Apart free microbial communities’ investigations, few biological studies have been leaded yet. Investigations of microbial communities associated with Nematoda, an ecologically important group in sediments, can help to improve our overall understanding of these ecosystems. We used a multidisciplinary-approach, based on microscopic observations (scanning electron microscopy: SEM and Fluorescence In Situ Hybridization: FISH) coupled with a molecular diversity analysis using metabarcoding, based on the 16S rRNA gene (V3-V4 region), to characterize the bacterial community of a free-living marine nematode and its environment, the shallow hydrothermal vent near Naples (Italy). Observations of living bacteria in the intestine (FISH), molecular and phylogenetic analyses showed that this species of nematode harbors its own bacterial community, distinct from the surrounding sediment and water. Metabarcoding results revealed the specific microbiomes of the sediment from three sites of this hydrothermal area to be composed mainly of sulfur oxidizing and reducing related bacteria

Multiscale structures of lipids in foods as parameters affecting fatty acid bioavailability and lipid metabolism.

This review is respectfully dedicated to the memory of Michel Ollivon, Research Director at CNRS (Châtenay-Malabry, France), outstanding physico-chemist specialist of lipid organization, recipient of the Hilditch Memorial Lecture award, who was the initiator of the network RMT LISTRAL. We are also sadly paying tribute to Jean-Luc Vendeuvre, Food Engineer at the French Pork and Pig Institute (IFIP, Maisons-Alfort, France), outstanding expert in meat products who participated actively in RMT LISTRAL and provided unpublished data for figures in the present review, who passed away during review submission. RMT LISTRAL: Mixed Technological Network combining academic and industrial partners, devoted to the enhancement and divulgation of knowledge regarding structured dietary lipids.International audienceOn a nutritional standpoint, lipids are now being studied beyond their energy content and fatty acid (FA) profiles. Dietary FA are building blocks of a huge diversity of more complex molecules such as triacylglycerols (TAG) and phospholipids (PL), themselves organised in supramolecular structures presenting different thermal behaviours. They are generally embedded in complex food matrixes. Recent reports have revealed that molecular and supramolecular structures of lipids and their liquid or solid state at the body temperature influence both the digestibility and metabolism of dietary FA. The aim of the present review is to highlight recent knowledge on the impact on FA digestion, absorption and metabolism of: (i) the intramolecular structure of TAG; (ii) the nature of the lipid molecules carrying FA; (iii) the supramolecular organization and physical state of lipids in native and formulated food products and (iv) the food matrix. Further work should be accomplished now to obtain a more reliable body of evidence and integrate these data in future dietary recommendations. Additionally, innovative lipid formulations in which the health beneficial effects of either native or recomposed structures of lipids will be taken into account can be foreseen

A Nematode of the Mid-Atlantic Ridge Hydrothermal Vents Harbors a Possible Symbiotic Relationship

Deep-sea hydrothermal vent meiofauna have been the focus of recent research and the discovery of an abundant well-adapted free-living marine nematode on the Mid-Atlantic Ridge offers new perspectives on adaptations to the vent environment. Indeed, knowledge concerning biological interactions of microbes and meiofauna in marine extreme environments is scarce, especially for nematodes. In this study, we used microscopic observations [fluorescence in situ hybridization (FISH) and scanning electron microscopy (SEM)] and metabarcoding of 16S rRNA to characterize the bacterial community of the nematode species Oncholaimus dyvae, an overlooked but ecologically important vent organism. Detection of bacteria in the buccal cavity and on the cuticle (SEM) and epibionts in its intestine (FISH) suggests that O. dyvae harbors its own bacterial community. Molecular results and phylogenetic analysis show that bacteria associated with this species are related to symbiotic lineages typical of hydrothermal vent fauna, such as sulfur-oxidizing bacteria related to Epsilonproteobacteria and Gammaproteobacteria. This multi-approach study suggests a potential symbiotic role of bacteria with its nematode host and opens new research perspectives on vent meiofauna

Pour une démocratie socio-environnementale : cadre pour une plate-forme participative « transition écologique »

Contribution publiée in Penser une démocratie alimentaire Volume II – Proposition Lascaux entre ressources naturelles et besoins fondamentaux, F. Collart Dutilleul et T. Bréger (dir), Inida, San José, 2014, pp. 87-111.International audienceL’anthropocène triomphant actuel, avec ses forçages environnementaux et sociaux, est à l’origine de l’accélération des dégradations des milieux de vie sur Terre et de l’accentuation des tensions sociales et géopolitiques. Passer à un anthropocène de gestion équitable, informé et sobre vis-à-vis de toutes les ressources et dans tous les secteurs d’activité (slow anthropocene), impose une analyse préalable sur l’ensemble des activités et des rapports humains. Cette transition dite « écologique », mais en réalité à la fois sociétale et écologique, est tout sauf un ajustement technique de secteurs dits prioritaires et technocratiques. Elle est avant tout culturelle, politique et philosophique au sens propre du terme. Elle est un horizon pour des trajectoires de développement humain, pour des constructions sociales et économiques, censées redéfinir socialement richesse, bien-être, travail etc. La dénomination « transition écologique » est largement véhiculée, mais ses bases conceptuelles ne sont pas entièrement acquises ni même élaborées. Dans ce contexte, les étudiants en première année de Master BioSciences à l’Ecole Normale Supérieure (ENS) de Lyon ont préparé une première étude analytique de ce changement radical et global de société pour mieux comprendre dans quelle société ils souhaitent vivre, en donnant du sens aux activités humaines présentes et à venir. Une trentaine de dossiers sur divers secteurs d’activités et acteurs de la société ont été produits et ont servis de support à cette synthèse. Plus largement, le but est de construire un socle conceptuel et une plate-forme de travail sur lesquels les questions de fond, mais aussi opérationnelles, peuvent être posées et étudiées en permanence. Cette démarche participative est ouverte à la collectivité sur le site http://institutmichelserres.ens-lyon.fr/

How β-Lactam Antibiotics Enter Bacteria: A Dialogue with the Porins

BACKGROUND:Multi-drug resistant (MDR) infections have become a major concern in hospitals worldwide. This study investigates membrane translocation, which is the first step required for drug action on internal bacterial targets. beta-lactams, a major antibiotic class, use porins to pass through the outer membrane barrier of Gram-negative bacteria. Clinical reports have linked the MDR phenotype to altered membrane permeability including porin modification and efflux pump expression. METHODOLOGY/PRINCIPAL FINDINGS: Here influx of beta-lactams through the major Enterobacter aerogenes porin Omp36 is characterized. Conductance measurements through a single Omp36 trimer reconstituted into a planar lipid bilayer allowed us to count the passage of single beta-lactam molecules. Statistical analysis of each transport event yielded the kinetic parameters of antibiotic travel through Omp36 and distinguishable translocation properties of beta-lactams were quantified for ertapenem and cefepime. Expression of Omp36 in an otherwise porin-null bacterial strain is shown to confer increases in the killing rate of these antibiotics and in the corresponding bacterial susceptibility. CONCLUSIONS/SIGNIFICANCE: We propose the idea of a molecular "passport" that allows rapid transport of substrates through porins. Deciphering antibiotic translocation provides new insights for the design of novel drugs that may be highly effective at passing through the porin constriction zone. Such data may hold the key for the next generation of antibiotics capable of rapid intracellular accumulation to circumvent the further development MDR infections

Identification and Evolution of Drug Efflux Pump in Clinical Enterobacter aerogenes Strains Isolated in 1995 and 2003

BACKGROUND: The high mortality impact of infectious diseases will increase due to accelerated evolution of antibiotic resistance in important human pathogens. Development of antibiotic resistance is a evolutionary process inducing the erosion of the effectiveness of our arsenal of antibiotics. Resistance is not necessarily limited to a single class of antibacterial agents but may affect many unrelated compounds; this is termed 'multidrug resistance' (MDR). The major mechanism of MDR is the active expulsion of drugs by bacterial pumps; the treatment of gram negative bacterial infections is compromised due to resistance mechanisms including the expression of efflux pumps that actively expel various usual antibiotics (beta-lactams, quinolones, ...). METHODOLOGY/PRINCIPAL FINDINGS: Enterobacter aerogenes has emerged among Enterobacteriaceae associated hospital infections during the last twenty years due to its faculty of adaptation to antibiotic stresses. Clinical isolates of E. aerogenes belonging to two strain collections isolated in 1995 and 2003 respectively, were screened to assess the involvement of efflux pumps in antibiotic resistance. Drug susceptibility assays were performed on all bacterial isolates and an efflux pump inhibitor (PAbetaN) previously characterized allowed to decipher the role of efflux in the resistance. Accumulation of labelled chloramphenicol was monitored in the presence of an energy poison to determine the involvement of active efflux on the antibiotic intracellular concentrations. The presence of the PAbetaN-susceptible efflux system was also identified in resistant E. aerogenes strains. CONCLUSIONS/SIGNIFICANCE: For the first time a noticeable increase in clinical isolates containing an efflux mechanism susceptible to pump inhibitor is report within an 8 year period. After the emergence of extended spectrum beta-lactamases in E. aerogenes and the recent characterisation of porin mutations in clinical isolates, this study describing an increase in inhibitor-susceptible efflux throws light on a new step in the evolution of mechanism in E. aerogenes