Mont-Saint-Aignan, France
Mont-Saint-Aignan, France

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Lebrun J.D.,Laboratoire BioSol | Lebrun J.D.,French National Institute for Agricultural Research | Trinsoutrot-Gattin I.,Laboratoire BioSol | Vinceslas-Akpa M.,University of Rouen | And 4 more authors.
Soil Biology and Biochemistry | Year: 2012

Enzymes are known to be sensitive indicators of soil quality. Nevertheless, the natural variability of their activities needs to be considered for a relevant interpretation of activity levels, especially in contaminated soils. We first monitored the variability of enzymatic activities (acid and alkaline phosphatases, β-glucosidase, N-acetyl-β-glucosaminidase, urease and dehydrogenase) in two agricultural sites in north-western France during a seasonal April-October cycle. For both sites, two types of long-term different agricultural managements, grassland and intensive cropping were considered. Our results revealed great variability of enzymatic activities in space and over time, yet more pronounced for grassland than for cropped soils. Then, we assessed the impact of copper on enzymes activity on Terrestrial Model Ecosystems (TMEs) filled with undisturbed soil, and incubated for 70 days in open-field conditions. Copper was added at two concentration levels corresponding to a regulated annual agronomic input (2 mg kg -1) or to a high soil contamination (200 mg kg -1). In comparison to effects of natural spatiotemporal variability of soil conditions, copper addition did not show significant impacts on enzymatic activities. Finally, our results confirmed that for assessing effective impacts of contaminants in soils under real field conditions, natural spatiotemporal soil variability must be considered. © 2012 Elsevier Ltd.


Gangneux C.,Laboratoire BioSol | Akpa-Vinceslas M.,University of Rouen | Sauvage H.,Laboratoire BioSol | Desaire S.,Laboratoire BioSol | And 2 more authors.
Soil Biology and Biochemistry | Year: 2011

Twelve differently-managed silty soils from North-Western France were chosen to compare two common methods of quantifying soil microbial biomass: Chloroform fumigation and extraction-labile carbon (CL_C) and microbial double stranded DNA (dsDNA). We also determined the contributions of each of the fungal, bacterial, and plant kingdoms to the total community dsDNA using real-time Polymerase Chain Reaction with kingdom-specific ribosomal primer sets. Regardless of the method, the highest microbial biomasses were associated with long-term untilled plots. Site (locations) specificities could also be detected, especially in conventionally cultivated lands. Regardless of site, a strong linear relationship could be drawn between CL_C and dsDNA in tilled lands (r = 0.91, n = 15, P = 0.01) and in grasslands (r = 0.78, n = 21, P = 0.01). Moreover, we propose a logarithmic model describing all of our silty soils, irrespective of management. In order to explain the non-linearity (log) of this relationship, we tested the hypothesis of a weak plant dsDNA contribution in total dsDNA in comparison with the well-documented root cell contribution to CL_C quantifications. Plant dsDNA never exceeded 2.6% of total dsDNA content for all of the soils studied. Among groups examined, the bacterial dsDNA contribution to the community dsDNA pool was the most site- and/or pedoclimatic-dependent. Fungi constituted a major component of total microbial biomass in grassland or in land with permanent plant cover where their proportion reached almost 50% of total dsDNA. More precisely, fungal dsDNA concentration was highly related to tillage. Our study demonstrated the expediency of the total microbial dsDNA quantification in agricultural silty soils rather than the time-consuming quantification of CL_C. Quantifying the relative contribution of bacterial or fungal biomass in total dsDNA by real-time PCR allows to access to a new level of knowledge of the soil microbial biomass and to reveal the balances between those two kingdoms according to soils or farming practices. © 2010 Elsevier Ltd.


Lebrun J.D.,French National Institute for Agricultural Research | Lebrun J.D.,Laboratoire BioSol | Demont-Caulet N.,University Paris Diderot | Demont-Caulet N.,French National Institute for Agricultural Research | And 4 more authors.
Chemosphere | Year: 2011

The relationship between the expression of extracellular enzymatic system and a metal stress is scarce in fungi, hence limiting the possible use of secretion profiles as tools for metal ecotoxicity assessment. In the present study, we investigated the effect of Zn, Cu, Pb and Cd, tested alone or in equimolar cocktail, on the secretion profiles at enzymatic and protein levels in Trametes versicolor. For that purpose, extracellular hydrolases (acid phosphatase, β-glucosidase, β-galactosidase and N-acetyl-β-glucosaminidase) and ligninolytic oxidases (laccase, Mn-peroxidase) were monitored in liquid cultures. Fungal secretome was analyzed by electrophoresis and laccase secretion was characterized by western-blot and mass spectrometry analyses. Our results showed that all hydrolase activities were inhibited by the metals tested alone or in cocktail, whereas oxidase activities were specifically stimulated by Cu, Cd and metal cocktail. At protein level, metal exposure modified the electrophoretic profiles of fungal secretome and affected the diversity of secreted proteins. Two laccase isoenzymes, LacA and LacB, identified by mass spectrometry were differentially glycosylated according to the metal exposure. The amount of secreted LacA and LacB was strongly correlated with the stimulation of laccase activity by Cu, Cd and metal cocktail. These modifications of extracellular enzymatic system suggest that fungal oxidases could be used as biomarkers of metal exposure. © 2010 Elsevier Ltd.


Trap J.,IRD Montpellier | Hattenschwiler S.,CNRS Center of Evolutionary and Functional Ecology | Gattin I.,Laboratoire Biosol | Aubert M.,CNRS Biodiversity Studies Laboratory
Forest Ecology and Management | Year: 2013

The role of forest age as a potential driver of intraspecific variation in leaf litter quality, that is a key plant trait determining ecosystem functioning, has largely been neglected. Using a set of fully replicated pure beech (Fagus sylvatica) forest stands differing in age (15, 65, 95 and 130. years), we quantified the forest stand age related variability of twelve leaf litter quality traits. Litter Mg, N and K showed significantly higher concentrations in litter from 15-yrs-old stands and decreased with increasing stand age. Mn was the only nutrient analyzed that was highest in the oldest stands. Hemicellulose and cellulose were lowest, and lignin and lignin/N ratio were highest in stands of intermediate age. The amount of N within the litter lignin fraction was highest in the 95-yrs-old stands (51% of total N) and lowest in the oldest stands (34% of total N). The amount of N associated within the hemicellulose fraction (<3%) showed the opposite pattern along the forest stand age gradient compared to lignin. Using Partial Least Squares regressions, we showed that litter N, C/N, lignin/N, K, Mn and Mg were the most important predictors of litter decomposition along the chronosequence. In contrast the proportions of C fractions and the amount of N within these C fractions were the most significant variables explaining the variation in final litter N content after one year of decomposition. N mineralization in ground litter was highly related to the proportion of total N within lignin and humus N mineralization was mostly explained by Mn and the lignin/N ratio. We showed that forest age is an important driver of litter quality variation and contributed considerably to the overall variation of F. sylvatica leaf litter quality traits observed from a reviewed data of published studies conducted at the continental scale. Furthermore, intraspecific litter quality variation greatly impacted belowground processes. Accounting for forest age related litter trait variation, and for the crucial role of the distribution of N within different litter C fractions, may improve the mechanistic understanding of ecosystem functioning. © 2013 Elsevier B.V.


Niepceron M.,CNRS Laboratory of Microbiology Signals and Microenvironment | Niepceron M.,University of Rouen | Martin-Laurent F.,CNRS Agroecology Lab | Martin-Laurent F.,French National Institute for Agricultural Research | And 8 more authors.
Environmental Pollution | Year: 2013

The impact of a multiple contamination by polycyclic aromatic hydrocarbons (PAHs) was studied on permanent grassland soil, historically presenting low contamination (i.e. less than 1 mg kg-1). Soil microcosms were spiked at 300 mg kg-1 with either single or a mixture of seven PAHs. While total dissipation of the phenanthrene was reached in under 90 days, only 60% of the PAH mixture were dissipated after 90 days. Interestingly, after 30 days, the abundance of the GammaProteobacteria class (assessed by qPCR) become significantly higher in microcosms spiked with the PAH mixture. In addition, the specific abundance of the cultivable Pseudomonas spp., which belong to the GammaProteobacteria class, increased earlier and transiently (after 8 days) in the microcosms spiked with the PAH mixture. Consequently, we propose to use the GammaProteobacteria as a bioindicator to detect the impact on the bacterial community of a multiple contamination by PAHs in agricultural soils. © 2013 Elsevier Ltd. All rights reserved.


Cannesan M.A.,University of Rouen | Durand C.,University of Rouen | Burel C.,University of Rouen | Gangneux C.,Laboratoire BioSol | And 6 more authors.
Plant Physiology | Year: 2012

Root tips of many plant species release a number of border, or border-like, cells that are thought to play a major role in the protection of root meristem. However, little is currently known on the structure and function of the cell wall components of such root cells. Here, we investigate the sugar composition of the cell wall of the root cap in two species: pea (Pisum sativum), which makes border cells, and Brassica napus, which makes border-like cells. We find that the cell walls are highly enriched in arabinose and galactose, two major residues of arabinogalactan proteins. We confirm the presence of arabinogalactan protein epitopes on root cap cell walls using immunofluorescence microscopy. We then focused on these proteoglycans by analyzing their carbohydrate moieties, linkages, and electrophoretic characteristics. The data reveal (1) significant structural differences between B. napus and pea root cap arabinogalactan proteins and (2) a cross-link between these proteoglycans and pectic polysaccharides. Finally, we assessed the impact of root cap arabinogalactan proteins on the behavior of zoospores of Aphanomyces euteiches, an oomycetous pathogen of pea roots. We find that although the arabinogalactan proteins of both species induce encystment and prevent germination, the effects of both species are similar. However, the arabinogalactan protein fraction from pea attracts zoospores far more effectively than that from B. napus. This suggests that root arabinogalactan proteins are involved in the control of early infection of roots and highlights a novel role for these proteoglycans in root-microbe interactions. © 2012 American Society of Plant Biologists. All Rights Reserved.


Cannesan M.A.,University of Rouen | Gangneux C.,Laboratoire BioSol | Lanoue A.,CNRS Biomolecule and Plant Biotechnology Laboratory | Giron D.,CNRS Research Institute of Insect Biology | And 4 more authors.
Annals of Botany | Year: 2011

•Background and Aims: The oomycete Aphanomyces euteiches causes up to 80% crop loss in pea (Pisum sativum). Aphanomyces euteiches invades the root system leading to a complete arrest of root growth and ultimately to plant death. To date, disease control measures are limited to crop rotation and no resistant pea lines are available. The present study aims to get a deeper understanding of the early oomyceteplant interaction at the tissue and cellular levels. •Methods: Here, the process of root infection by A. euteiches on pea is investigated using flow cytometry and microscopic techniques. Dynamic changes in secondary metabolism are analysed with high-performance liquid chromatography with diode-array detection. •Key Results: Root infection is initiated in the elongation zone but not in the root cap and border cells. Border-cell production is significantly enhanced in response to root inoculation with changes in their size and morphology. The stimulatory effect of A. euteiches on border-cell production is dependent on the number of oospores inoculated. Interestingly, border cells respond to pathogen challenge by increasing the synthesis of the phytoalexin pisatin. •Conclusions: Distinctive responses to A. euteiches inoculation occur at the root tissue level. The findings suggest that root border cells in pea are involved in local defence of the root tip against A. euteiches. Root border cells constitute a convenient quantitative model to measure the molecular and cellular basis of plantmicrobe interactions. © The Author 2011. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.


Trap J.,Laboratoire Biosol | Riah W.,Laboratoire Biosol | Akpa-Vinceslas M.,CNRS Biodiversity Studies Laboratory | Bailleul C.,Laboratoire Biosol | And 2 more authors.
Soil Biology and Biochemistry | Year: 2012

We tested the relevance of the microplate fluorimetric (F) assay for five enzymes in contrasting land uses, including woodland, grassland, cultivated and contaminated lands, as compared to the standard spectrophotometric (P) method. Enzymatic activity measured by the P method ranged from 0 to 56.04nmol-pNPg -1min -1 (median=4) while the F method revealed lower values ranging from 0 to 6.22nmol-MUBg -1 dry soil min -1 (median=1). The values obtained by the P method were around 8 times higher than those revealed by the F method. However, the F method revealed significant differences in enzyme activity in orchard parcels (land use with low variations in soil properties). We concluded that the F method improves the effectiveness and the efficiency of measuring universal soil quality indicators using enzymes. © 2011 Elsevier Ltd.


Trap J.,Laboratoire Biosol | Laval K.,Laboratoire Biosol | Akpa-Vinceslas M.,CNRS Biodiversity Studies Laboratory | Gangneux C.,Laboratoire Biosol | And 3 more authors.
Soil Biology and Biochemistry | Year: 2011

We aimed to characterize humus macro-morphology and the associated soil microbial community within the unmodified litter (OL), the fragmented and humified layers (FH) and the organo-mineral (A) layer along a beech (Fagus sylvatica L.) forest chronosequence with four stand age-classes (15-, 65-, 95-, 130-yr-old) in Normandy, France. Humus macro-morphology was described with 36 quantitative and semi-quantitative variables. We measured microbial biomass N (Nmic), microbial N quotient (Nmic-to-Nt), fungal ergosterol, bacterial and fungal DNA using 16S and 18S rDNA real-time qPCR and evaluated the potential metabolic profile of heterotrophic bacteria within each soil layer and stand age-class. The log-transform ergosterol/fungal DNA ratio (EFR index) was used as an indicator related to active fungal biomass and the fungal/bacterial (F/B) ratio was calculated from qPCR results. There was a shift from mull (mainly dysmull) to moder humus forms along the chronosequence. While the Nmic did not change significantly, the Nmic-to-Nt decreased along the chronosequence in the OL layer. Ergosterol content increased in FH and A layers and the F/B ratio increased in the FH layer with increasing beech forest age. The EFR index was significantly higher in the OL and A layers of the oldest stands, whereas the highest EFR index in the FH layer occurred in the 15-yr-old stands. The functional diversity of heterotrophic bacteria was greater within OL and FH layers of 130-yr-old stands, but highest in the A layer of 15-yr-old stands while the Average Well Color Development remained stable for all soil layers. We found significant correlations between macro-morphology and microbial variables, especially between FH-based morphology and fungal biomass. Our main results are that beech forest maturation is accompanied by (1) an increase in fungal biomass in the FH layers and, (2) an increase in heterotrophic bacteria functional diversity in the organic layers. We have identified key macro-morphology variables that are good predictors of the structural and functional profile of the soil microbial community during beech forest development. © 2011 Elsevier Ltd.


Trap J.,Laboratoire Biosol | Trap J.,Institute Of Recherche Pour Le Daveloppement | Bureau F.,CNRS Biodiversity Studies Laboratory | Perez G.,CNRS Biodiversity Studies Laboratory | Aubert M.,CNRS Biodiversity Studies Laboratory
Soil Biology and Biochemistry | Year: 2013

Using Partial Least Squares regression, we ranked the ability of leaf litter and topsoil properties to predict humus form shift along a 130-yr-old pure beech forest chronosequence. Three models were tested, including only litter properties (model 1), only topsoil properties (model 2) and both litter and topsoil properties (model 3). The first model was highly significant and explained more than 91% of the humus form variability with N-based variables, Mn, Mg and K as the best predictors. The second model showed lower goodness of fit (75%) with Ca and Mg contents, pHKCl and ΔpH as good predictors. The last model showed that litter traits were better predictors compared to topsoil variables, suggesting that beech trees may impact humus form along forest development mainly through aboveground pathways. © 2012 Elsevier Ltd.

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