Analyse multi-résidus de contaminants organiques exogènes dans des sols

National audienc

Shared active site architecture between archaeal PolD and multi-subunit RNA polymerases revealed by X-ray crystallography

International audienceArchaeal replicative DNA polymerase D (PolD) constitute an atypical class of DNA polymerases made of a proofreading exonuclease subunit (DP1) and a larger polymerase catalytic subunit (DP2), both with unknown structures. We have determined the crystal structures of Pyrococcus abyssi DP1 and DP2 at 2.5 and 2.2 Å resolution, respectively, revealing a catalytic core strikingly different from all other known DNA polymerases (DNAPs). Rather, the PolD DP2 catalytic core has the same 'double-psi b-barrel' architecture seen in the RNA polymerase (RNAP) superfamily, which includes multi-subunit transcriptases of all domains of life, homodimeric RNA-silencing pathway RNAPs and atypical viral RNAPs. This finding bridges together, in non-viral world, DNA transcription and DNA replication within the same protein superfamily. This study documents further the complex evolutionary history of the DNA replication apparatus in different domains of life and proposes a classification of all extant DNAPs

Devenir et transfert des cyanotoxines de type microcystine dans un système sol-plante

Devenir et transfert des cyanotoxines de type microcystine dans un système sol-plante. 5ème Séminaire des Ecotoxicologues de l’INR

Evaluation of the transfer and the accumulation of microcystins in tomato (Solanum lycopersicum cultivar MicroTom) tissues using a cyanobacterial extract containing microcystins and the radiolabeled microcystin-LR (14C-MC-LR)

Microcystins are the most common cyanotoxins and may be expected wherever blooms of cyanobacteria occur in surface waters. Their persistence both in the irrigation water and in the soil can lead to their transfer and bioaccumulation into agricultural plants. The aim of this work was to investigate microcystin accumulation in Solanum lycopersicum cultivar MicroTom. The plant was exposed to either Microcystis aeruginosa crude extracts containing up to 100 μg eq. MC-LR L− 1 in a soil–plant system for 90 days or pure radiolabeled 14C-MC-LR in a hydroponic condition for 48 h. Toxin bioaccumulation in the soil and different plant tissues was assessed both by the PP2A inhibition assay and by liquid chromatography-mass spectrometry (LC/MS/MS). After 90 days of exposure, microcystins persisted in the soil and their free extractable concentrations accumulated were very low varying between 1.6 and 3.9 μg eq. MC-LR kg− 1 DW. Free MC-LR was detected only in roots and leaves with concentrations varying between 4.5 and 8.1 μg kg− 1 DW and between 0.29 and 0.55 μg kg− 1 DW, respectively. By using radioactivity (14C-MC-LR), the results have reported a growing accumulation of toxins within the organs roots > leaves > stems and allowed them to confirm the absence of MC-LR in fruits after 48 h of exposure. The bioconcentration factor (BCF) was 13.6 in roots, 4.5 in leaves, and 1.4 in stems. On the other hand, the results highlight the presence of two radioactive fractions in different plant tissues. The non-extractable fraction of radioactivity, corresponding to the covalently bound MC-LR, was higher than that of the extractable fraction only in roots and leaves reaching 56% and 71% of the total accumulated toxin, respectively. Therefore, results raise that monitoring programs must monitor the presence of MCs in the irrigation water to avoid the transfer and accumulation of these toxins in crops

Centennial fertilization-induced soil processes control contemporary soil geochemistry. Lessons from a long-term bare fallow experiment

Centennial fertilization-induced soil processes control contemporary soil geochemistry. Lessons from a long-term bare fallow experiment. 14èmes Journées d'Etudes des Sol

Centennial fertilization-induced soil processes control contemporary soil geochemistry. Lessons from a long-term bare fallow experiment

Centennial fertilization-induced soil processes control contemporary soil geochemistry. Lessons from a long-term bare fallow experiment. Rothamsted Research Work shop: “The Future of Long-Term Experiments in agricultural science

Does pH influence soil hydro-mechanical properties?

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Evaluation of epoxiconazole bioavailability in soil to the earthworm Aporrectodea icterica

In soil, the determination of total concentration using an exhaustive extraction method is not relevant to evaluate the exposure of an organism to a chemical, because of sorption processes. However, little attention has been paid to the bioavailability of organic contaminants to earthworms, and to their effect on sensitive earthworm species found in cultivated fields, such as Aporrectodea icterica [1]. As ecosystem engineers, earthworms influence soil structure and chemistry and are thus key-organisms for the health of terrestrial ecosystems. However, they can be threatened by contaminants such as the fungicide epoxiconazole, which is persistent in soil and presents a chronic toxicity even towards a resistant earthworm species (Eisenia fetida) at a concentration close to the recommended dose. This study aimed to propose a mild extraction method to evaluate the bioavailability of the fungicide epoxiconazole to the earthworm Aporrectodea icterica [2]. Experiments were conducted in soils presenting various textures and organic carbon contents, spiked with formulated epoxiconazole 7 to 56 days prior to their extraction at one-fold to ten-fold the recommended dose. In parallel, the epoxiconazole concentration was determined in exposed earthworms. All the analysis were performed by UHPLCMS/ MS. The fungicide’s effects were evaluated by measuring weight gain, enzymatic activities and total protein contents. The proposed method to evaluate bioavailability was based on the pesticide entrapment in the cavity of hydroxypropyl-?-cyclodextrin, thus fulfilling the criteria of the ISO 17402 norm [3]. Furthermore, this mild method was demonstrated to be sensitive to soil sorption capacities and to ageing. The mild extraction method was then applied to explore the relationship between total and bioavailable concentrations in soil and in A. icterica, over 7 or 28 days exposure time. This demonstrated the proportionality between epoxiconazole concentration in earthworm and available in soil (up to 96%, with regression coefficient R2 0.98). Sublethal effects on earthworm remained not significant. References 1. C. Pelosi, S. Joimel, D. Makowski, 2013. Chemosphere 90, 895-900 2. S. Nélieu, G. Delarue, E. Ollivier, P. Awad, F. Fraillon, C. Pelosi, Environ. Sci. Pollut. Res. In Press DOI 10.1007/s11356-015-5270-4 3. ISO 17402, 2008. Soil quality - Guidance for the selection and application of methods for the assessment of bioavailability of contaminants in soil and soil material

Sublethal effects of epoxiconazole on the earthworm Aporrectodea icterica

Avec nos remerciements à Jodie Thénard, Virginie Grondin, Jean-Pierre Pétraud, Amélie Trouvé, Christelle Marrauld et Françoise PoirouxEarthworms play a key role in agroecosystem soil processes. This study aims to assess the effects of different doses of a commercial formulation of epoxiconazole (Opus®), a persistent and widely used fungicide, on the earthworm Aporrectodea icterica. A laboratory study was conducted in a natural soil in order to measure effects of Opus® on earthworm mortality, uptake, weight gain, enzymatic activities (catalase and glutathione-S-transferase), and energy resources (lipids and glycogens). The estimated LC50 was 45.5 mg kg−1, or 268 times the recommended dose. Weight gains were 28, 19, and 13 % of the initial weight after 28 days of exposure in the control and D1 and D10 (1 and 10 times the recommended dose) treatments, respectively. No difference was observed for catalase activity between the three treatments, at 7, 14, or 28 days. The glutathion-S-transferase (GST) activity was two times as high in D1 as in D0 at 14 days. At 28 days, glycogen concentration was lower in D10 than in the D1 treatment. This study highlighted moderate sublethal effects of the commercial formulation Opus® for earthworms. Considering that these effects were observed on a species found in cultivated fields, even at recommended rates, much more attention should be paid to this pesticide