Residual Doping in Homoepitaxial Zinc Oxide Layers Grown by Metal Organic Vapor Phase Epitaxy

International audienceFull maximum entropy mobility spectrum analysis was carried out on the basis of temperature and magneticfield- dependent Hall measurements to assess the transport properties of homoepitaxial metal organic vapor phase epitaxy zinc oxide layers. Two different conductivity channels were clearly identified and the channel with higher mobility and higher carrier concentration is associated with the epitaxial layer. Hydrogen impurity acting as residual donor and as a passivating species for acceptors is proposed to explain the higher carrier concentration and mobility in the epilayer. In contrast to heteroepitaxial layers, no conduction channel is observed from the substrate to epilayer interface

Carbapenem-Resistant Bacteria Recovered from Faeces of Dairy Cattle in the High Plains Region of the USA

OBJECTIVE:A study was conducted to recover carbapenem-resistant bacteria from the faeces of dairy cattle and identify the underlying genetic mechanisms associated with reduced phenotypic susceptibility to carbapenems. METHODS:One hundred and fifty-nine faecal samples from dairy cattle were screened for carbapenem-resistant bacteria. Phenotypic screening was conducted on two media containing ertapenem. The isolates from the screening step were characterised via disk diffusion, Modified Hodge, and Carba NP assays. Carbapenem-resistant bacteria and carbapenemase-producing isolates were subjected to Gram staining and biochemical testing to include Gram-negative bacilli. Whole genome sequencing was performed on bacteria that exhibited either a carbapenemase-producing phenotype or were not susceptible to ertapenem and were presumptively Enterobacteriaceae. RESULTS:Of 323 isolates collected from the screening media, 28 were selected for WGS; 21 of which were based on a carbapenemase-producing phenotype and 7 were presumptively Enterobacteriaceae and not susceptible to ertapenem. Based on analysis of WGS data, isolates included: 3 Escherichia coli harbouring blaCMY-2 and truncated ompF genes; 8 Aeromonas harbouring blacphA-like genes; 1 Acinetobacter baumannii harbouring a novel blaOXA gene (blaOXA-497); and 6 Pseudomonas with conserved domains of various carbapenemase-producing genes. CONCLUSIONS:Carbapenem resistant bacteria appear to be rare in cattle. Nonetheless, carbapenem-resistant bacteria were detected across various genera and were found to harbour a variety of mechanisms conferring reduced susceptibility. The development and dissemination of carbapenem-resistant bacteria in livestock would have grave implications for therapeutic treatment options in human medicine; thus, continued monitoring of carbapenem susceptibility among enteric bacteria of livestock is warranted

Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina

International audienceBackground: The understanding of enzymatic polysaccharide degradation has progressed intensely in the past few years with the identification of a new class of fungal-secreted enzymes, the lytic polysaccharide monooxygenases (LPMOs) that enhance cellulose conversion. In the fungal kingdom, saprotrophic fungi display a high number of genes encoding LPMOs from family AA9 but the functional relevance of this redundancy is not fully understood. Results: In this study, we investigated a set of AA9 LPMOs identified in the secretomes of the coprophilous ascomycete Podospora anserina, a biomass degrader of recalcitrant substrates. Their activity was assayed on cellulose in synergy with the cellobiose dehydrogenase from the same organism. We showed that the total release of oxidized oligosaccharides from cellulose was higher for PaLPMO9A, PaLPMO9E, and PaLPMO9H that harbored a carbohydrate-binding module from the family CBM1. Investigation of their regioselective mode of action revealed that PaLPMO9A and PaLPMO9H oxidatively cleaved at both C1 and C4 positions while PaLPMO9E released only C1-oxidized products. Rapid cleavage of cellulose was observed using PaLPMO9H that was the most versatile in terms of substrate specificity as it also displayed activity on cello-oligosaccharides and beta-(1,4)-linked hemicellulose polysaccharides (e.g., xyloglucan, glucomannan). Conclusions: This study provides insights into the mode of cleavage and substrate specificities of fungal AA9 LPMOs that will facilitate their application for the development of future biorefineries

L'Estellon (Baronnies, France), une "Pierre de Rosette" pour la biostratigraphie de l'Urgonien

Des associations d'organismes habituellement caractéristiques de faibles tranches d'eau (des orbitolinidés et des algues, en particulier) ont été identifiées dans des faciès relativement profonds de la "fosse vocontienne" (SE de la France), où ces éléments ont été transportés gravitairement et précocement resédimentés. Dans un tel contexte paléoenvironnemental, ces associations benthiques peuvent être directement calibrées sur les zones d'ammonites. D'après ces nouvelles observations, entre autres résultats, la première apparition de Palorbitolina lenticularis ainsi que celles de quatre représentants du genre Orbitolinopsis, soi-disant typiques de l'Aptien inférieur, sont datées du Barrémien inférieur. De fait la plupart des espèces d'orbitolinidés connues dans le Barrémien supérieur sont déjà présentes au Barrémien inférieur à L'Estellon. Concernant les plates-formes urgoniennes, les schémas de corrélations couramment utilisés, qui s'appuient sur des distributions biaisées (tronquées) d'orbitolinidés -- et par conséquent les conclusions et hypothèses qui en sont dérivées --, nécessitent au moins des révisions en profondeur, sinon un rejet définitif.Shallow-water assemblages of transported ("freshly reworked") bioclasts (mainly orbitolinids and dasycladales) are observed in the deeper facies of the "Vocontian Trough" (SE France). There these benthic assemblages can be directly correlated with ammonite zones. These new finds give an Early Barremian age to the earliest record of Palorbitolina lenticularis as well as those of four so-called "typical Early Aptian" representatives of the genus Orbitolinopsis. Actually most orbitolinid species recorded from the Late Barremian interval are now found present in Lower Barremian strata at L'Estellon. Some currently used correlation schemes for the Urgonian platforms, that are based on partial stratigraphic distribution ranges for the orbitolinids, --and consequently derived conclusions and hypotheses- - require at least in-depth revisions when they are not definitively refuted.The study of the ammonite fauna in the L'Estellon section (Drôme department, SE France) allows us to date episodes with gravitational deposition in this area of the "Vocontian Trough". They span most of the Barremian Stage, from the Nicklesi Zone up to the Giraudi Zone. We did not identify any Bedoulian redeposits, the "Bedoulian ridge" auct. being latest Barremian in age

GSSP proposal for the upper Aptian substage in the Apt Basin (Vaucluse, SE France): Synthesis of the stratigraphic data

La synthèse des données stratigraphiques recueillies depuis plus d'une décennie dans la région stratotypique a permis d'établir une coupe composite des "marnes aptiennes" s'étageant de la Sous-Zone d'ammonites à Grandis jusqu'à la base de la Zone à Melchioris, soit depuis la Zone de foraminifères à Schackoina (Leupoldina) gr. cabri jusqu'à la Zone à Globigerinelloides algerianus. Cette coupe composite intègre les coupes partielles de Clavaillan, Pichouraz Sud et Est, La Tuilière, Les Gays et Gargas (Vaucluse, SE France). Notre révision a montré en particulier que le banc marno-calcaire, rapproché du "Niveau blanc" vocontien et jusqu'alors supposé unique et isochrone, qui divise la série marneuse affleurant dans les coupes de Clavaillan et de Pichouraz, correspond en fait à deux niveaux stratigraphiquement distincts. La présente étude confirme que la série visible des marnes aptiennes dans la région stratotypique, non compte tenu de la Formation supra-urgonienne "A1" de Leenhardt (1883), ne comprend que les termes sommitaux du Bédoulien et une partie inférieure (= Gargasien inférieur et moyen) de l'Aptien s.s. (i.e., sensu Orbigny, 1840). Étayée par une approche intégrée, la mise en parallèle de la série du Bassin d'Apt avec les termes contemporains du Bassin de Cassis-La Bédoule a également permis de détecter et de quantifier des variations importantes, non concomitantes, des rythmes d'accumulation sédimentaire entre les deux secteurs. Au final, la coupe de Clavaillan, située à 8 km à l'WSW de Gargas, constitue l'unique affleurement où la limite entre la Sous-Zone à Grandis et la Zone à Furcata est visible dans un contexte permettant de le proposer comme candidat à la fixation du GSSP du sous-étage Gargasien (ou de l'Aptien s.s. dans sa conception historique).The synthesis of the stratigraphic data collected over more than a decade in the stratotypic area has made it possible to establish a composite section of the "Aptian marls" from the Grandis ammonite Subzone to the base of the Melchioris Zone, i.e., from the Schackoina (Leupoldina) gr. cabri foraminiferal Zone to the Globigerinelloides algerianus Zone. This composite section includes the partial sections from Clavaillan, South and East Pichouraz, La Tuilière, Les Gays and Gargas (Vaucluse, SE France). In particular, our revision has shown that the marly calcareous bed, which divides the marly series of Clavaillan and Pichouraz, compared with the Vocontian "Niveau blanc" and thought to be unique and isochronous, corresponds in fact to two stratigraphically distinct levels. The present study confirms that the visible series of marls in the stratotypic area, not taking into account the "A1" supra-Urgonian formation of Leenhardt (1883), includes only the uppermost terms of the Bedoulian and the lower terms (= Lower and Middle Gargasian) of the Aptian s.s. (i.e., sensu Orbigny, 1840). Based on the methods of integrated stratigraphy, a comparison of the series of the Apt Basin with the contemporary terms of the Cassis-La Bédoule Basin has also made it possible to detect and quantify important variations in the rhythms of sedimentary accumulation between the two sectors. In the end, the Clavaillan section, located 8 km WSW from the Gargas section, is the only outcrop where the boundary between the Grandis Subzone and the Furcata Zone is visible in a context which supports a proposal that this exposure be a candidate for the GSSP of the Gargasian substage (or of the Aptian s.s. in the initial concept of the creator of the stage)

Lytic xylan oxidases from wood-decay fungi unlock biomass degradation

Wood biomass is the most abundant feedstock envisioned for the development of modern biorefineries. However, the cost-ef-fective conversion of this form of biomass into commodity products is limited by its resistance to enzymatic degradation. Here we describe a new family of fungal lytic polysaccharide monooxygenases (LPMOs) prevalent among white-rot and brown-rot basidiomycetes that is active on xylans—a recalcitrant polysaccharide abundant in wood biomass. Two AA14 LPMO members from the white-rot fungus Pycnoporus coccineus substantially increase the efficiency of wood saccharification through oxida-tive cleavage of highly refractory xylan-coated cellulose fibers. The discovery of this unique enzyme activity advances our knowledge on the degradation of woody biomass in nature and offers an innovative solution for improving enzyme cocktails for biorefinery applications

The Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA)

To explore the various couplings across space and time and between ecosystems in a consistent manner, atmospheric modeling is moving away from the fractured limited-scale modeling strategy of the past toward a unification of the range of scales inherent in the Earth system. This paper describes the forward-looking Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA), which is intended to become the next-generation community infrastructure for research involving atmospheric chemistry and aerosols. MUSICA will be developed collaboratively by the National Center for Atmospheric Research (NCAR) and university and government researchers, with the goal of serving the international research and applications communities. The capability of unifying various spatiotemporal scales, coupling to other Earth system components, and process-level modularization will allow advances in both fundamental and applied research in atmospheric composition, air quality, and climate and is also envisioned to become a platform that addresses the needs of policy makers and stakeholders