University of Rouen

About: University of Rouen is a education organization based out in Rouen, France. It is known for research contribution in the topics: Population & Receptor. The organization has 7299 authors who have published 13209 publications receiving 313477 citations.

Home-Field Advantage: A matter of interaction between litter biochemistry and decomposer biota

Abstract: Home-Field Advantage (HFA) defines the way with which a plant litter may decompose faster in the habitat from which it derives (i.e. home) than beneath a different plant community (i.e. away from home). Recent studies, using plurispecific litter and involving several soil biota groups, failed to demonstrate a clear positive HFA effect. The interactions between different soil biota groups and different litter types may cause additive effect on decomposition process. Concomitantly, new hypothesis was raised which expects a continuum from positive to negative interactions between transplanted litter and host litter as both litters become increasingly dissimilar in quality, which has been called Substrate quality–Matrix quality Interaction (SMI). Against this background, we aimed at testing the influence of both litter quality and soil organisms in determining the HFA and the SMI hypothesis. We used reciprocal plurispecific transplanting litter along a gradient of litter quality with three successional stages: early (S1), medium (S2) and late successional stage (S3), coupled with litterbags of different mesh size to select different decomposers communities. Furthermore, we analyzed litter quality in order to test the SMI hypothesis. Overall, we did not observe a general HFA or SMI effect. In micromesh litterbags, only S1 litter showed an HFA effect (+7%) while in mesomesh litterbags, only S2 litter presented an HFA effect (+8%). The contribution of each litter quality fraction to the HFA index allowed us to show that only highly labile fractions (i.e., solubles and hemicellulose) presented a positive HFA index, independently of the mesh size. Indeed, our findings corroborated the SMI hypothesis but for labile fraction only. Finally, our results highlighted a strong inertia between different soil decomposer groups for the attack of the most recalcitrant biochemical fraction (i.e. lignin) only in late stage, independently of the litter origin.

Atomic structure of hardening precipitates in an Al–Mg–Zn–Cu alloy determined by HAADF-STEM and first-principles calculations: relation to η-MgZn2

Abstract: The structures of two nanoscale plate precipitates prevalent at maximum strength and over-aged conditions in a 7449 Al–Mg–Zn–Cu alloy were investigated. Models derived from images of high angle annular dark field scanning transmission electron microscopy were supported by first-principles calculations. Both structures are closely linked to the η-MgZn2 Laves phase through similar layers of a rhombohedral atomic subunit. The finest plate contains one such layer together with a layer of an orthorhombic unit. The second plate contains rhombohedral layers only, normally four, but rotated relatively to form different stacking variants, one of which may be likened to η. For both structures, the same atomic planes describe the main interface with Al. Both plates could be described in space group P3. The unit cells comprise interface and arbitrary numbers of {111}Al (habit) planes. Eight Al-planes were included in the first-principles calculations. The enthalpy indicates high layer/unit stability. The plate thickness can be understood by a simple mismatch formulation.

Comparative Genomics of Environmental and Clinical Stenotrophomonas maltophilia Strains with Different Antibiotic Resistance Profiles

Abstract: Stenotrophomonas maltophilia, a ubiquitous Gram-negative γ-proteobacterium, has emerged as an important opportunistic pathogen responsible for nosocomial infections. A major characteristic of clinical isolates is their high intrinsic or acquired antibiotic resistance level. The aim of this study was to decipher the genetic determinism of antibiotic resistance among strains from different origins (i.e., natural environment and clinical origin) showing various antibiotic resistance profiles. To this purpose, we selected three strains isolated from soil collected in France or Burkina Faso that showed contrasting antibiotic resistance profiles. After whole-genome sequencing, the phylogenetic relationships of these 3 strains and 11 strains with available genome sequences were determined. Results showed that a strain's phylogeny did not match their origin or antibiotic resistance profiles. Numerous antibiotic resistance coding genes and efflux pump operons were revealed by the genome analysis, with 57% of the identified genes not previously described. No major variation in the antibiotic resistance gene content was observed between strains irrespective of their origin and antibiotic resistance profiles. Although environmental strains generally carry as many multidrug resistant (MDR) efflux pumps as clinical strains, the absence of resistance-nodulation-division (RND) pumps (i.e., SmeABC) previously described to be specific to S. maltophilia was revealed in two environmental strains (BurA1 and PierC1). Furthermore the genome analysis of the environmental MDR strain BurA1 showed the absence of SmeABC but the presence of another putative MDR RND efflux pump, named EbyCAB on a genomic island probably acquired through horizontal gene transfer.