Phytoextraction process optimization : characterization of the soil bacteria flora associated to the hyperaccumulator Arabidopsis halleri

International audiencePhytotechnologies are microbial-assisted techniques that use living plants for the treatment of contaminated sites. Among these, phytoextraction based on hyperaccumulator plants such as Arabidopsis halleri, may be an option to remove trace elements in soil. One method to optimize Arabidopsis halleri's phytoextraction is the inoculation of plant roots by plant growth promoting bacteria (PGPB). In this study, we analyzed the total bacterial diversity in a Zn and Cd contaminated industrial soil (Auby, France) with restriction fragment length polymorphism (RFLP). Preliminary results showed a large bacterial diversity in Auby's soil. Cultivable bacteria were isolated and characterized for their PGPB traits (ACC deaminase activity, siderophores and Indol-Acetic-Acid (IAA) productions). Bacteria that will answer positively to the three PGPB tests will be preferentially selected, and inoculated to Arabidopsis halleri roots. Bacteria effects on plant biomass and/or accumulating yield will be presented

Optimisation de la phytoextraction : caractérisation et sélection de bactéries PGPB associées à une plante hyperaccumulatrice de Zn et Cd : Arabidopsis halleri

National audiencePhytotechnologies are microbial-assisted techniques that use living plants for the treatment of contaminated sites. Among these, phytoextraction based on hyperaccumulator plants such as Arabidopsis halleri, may be an option to remove trace elements in soil. One method to optimize Arabidopsis halleri phytoextraction is the inoculation of plant roots by plant growth promoting bacteria (PGPB). In this study, we proposed a protocol for sampling bacteria in three different soil fractions neared root system of Arabidopsis halleri: global, rhizospheric and rhizoplan. The cultivable bacteria were isolated for a Zn and Cd contaminated industrial soil (Auby, France) and were isolated and characterized for their PGPB traits : 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, siderophores and Indol-Acetic-Acid (IAA) productions). Bacteria answering positively to the three PGPB tests have been preferentially selected to be inoculated to Arabidopsis halleri root system. Bacteria effects on plant biomass and/or accumulating yield will be presented.Les phytotechnologies consistent en l'utilisation de plantes qui, par leur association avec la microflore du sol, ont la capacité de dépolluer les sites contaminés (eau, sol, sédiments). Parmi ces technologies, la phytoextraction, basée sur l'utilisation de plantes hyperaccumulatrices telle qu'Arabidopsis halleri, semble être une option pour décontaminer les sols pollués en éléments traces métalliques. Une des voies d'amélioration de la phytoextraction d'A. halleri serait l'inoculation du système racinaire de la plante par des bactéries capables de stimuler la croissance végétale (PGPB pour Plant Growth Promoting Bacteria). Dans cette étude, nous proposons un protocole d'échantillonnage des différentes fractions de sol autour de la racine : sols global, rhizosphérique et rhizoplan. Les bactéries cultivables, collectées sur un sol industriel contaminé en Zn et Cd (Auby, France), ont été isolées et analysées pour leurs caractéristiques PGPB : activité 1-aminocyclopropane-1-carboxylate (ACC) désaminase, productions de sidérophores et d'acide indole acétique (IAA). Les bactéries qui présentent trois caractères PGPB ont été préférentiellement sélectionnées pour être inoculées au niveau du système racinaire d'Arabidopsis halleri. Les effets de ces bactéries sur les paramètres de croissance de la plante et sa biomasse ou sur le rendement d'accumulation des éléments traces métalliques seront présentés

Study of the potential valorization of metal contaminated Salix via phytoextraction by combustion

International audiencePhytoextraction is an emerging technology to remediate soils and sediments contaminated with trace elements. In the particular case of dredged sediment landfill sites contaminated with metals, phytoextraction may contribute to the management scheme of sediments and to the revaluation of certain land-disposed contaminated sediments. In this study, rapidly growing trees (willows) were cultivated in short rotation coppice (SRC) on a metal contaminated dredged sediment landfill site to produce biomass for heat and financial return. Three willow clones were planted on 4.5 hectares of this disposal site to assess phytoextraction efficiency and biomass production. Two combustion assays were performed in a biomass boiler of 30 KW, the first one with Salix Zn and Cd enriched wood harvested from the SRC and the second one with Salix wood bought at a wood producer (control). Combustibles, ashes and gases were analyzed to study trace element behaviour during the combustion process. For phytoextraction efficiency, best results are obtained when exportation of both stems and leaves are carried out. The most optimistic scenario led to a reduction of the total Cd content of the sediment from 3.16 to 2 mg kg -1 in 23 years. Due to boiling points, Cd and Zn were more found in fumes than in ashes. According to current regulation, Salix wood issued from phytoextraction should be used for non-domestic purpose, in industrial or collective boilers equipped with efficient filters

Cd localisation and speciation in a contaminated sediment and in the Znand Cd hyperaccumulating plant Arabidopsis halleri

International audienceThe purpose of this work was to characterise the chemical speciation of Cd in a Zn- and Cd-contaminated dredged sediment subjected to a phytoremediation treatment with the hyperaccumulator plant Arabidopsis halleri

Phytostabilisation d'un site pollué par les éléments traces : opération pilote et pérennité du traitement

National audienceGrâce à l'utilisation combinée de plantes et d'agents immobilisants, la phytostabilisation assistée limite les risques associés à un sol contaminé en réduisant la biodisponibilité des polluants. Le rôle des plantes est de réduire le lessivage et l'érosion. En Europe et dans le monde, de nombreux sites ont déjà été phytostabilisés avec succès. Cependant, peu de projets de phytostabilisation associent une surface et une durée d'expérimentation suffisantes pour établir l'efficacité sur le long terme et en conditions réelles d'une telle pratique pour la gestion d'un site pollué. La nécessité de conduire des opérations pilotes sur une longue durée a été ainsi mise en avant par la communauté scientifique. L'objectif de ce projet mené sur un dispositif pilote mis en place en 2002 est d'estimer l'efficacité dans le temps d'une phytostabilisation assistée appliquée à un sédiment pollué par les éléments traces (Cd, Zn, Pb, Cu, As). Les paramètres suivis dans cette étude sont liés aux plantes initialement semées, aux espèces végétales venues spontanément coloniser le dispositif, aux agents immobilisants utilisés et aux caractéristiques physico-agronomiques de la matrice polluée. Une synthèse des résultats obtenus sur 7 années de suivi sera présentée lors du colloque

Metal immobilization and soil amendment efficiency at a contaminated sediment landfill site: a field study focusing on plants, springtails, and bacteria

International audienceMetal immobilization may contribute to the environmental management strategy of dredged sediment landfill sites contaminated by metals. In a field experiment, amendment effects and efficiency were investigated, focusing on plants, springtails and bacteria colonisation, metal extractability and sediment ecotoxicity. Conversely to hydroxylapatite (HA, 3% DW), the addition of Thomas Basic Slag (TBS, 5% DW) to a 5-yr deposited sediment contaminated with Zn, Cd, Cu, Pb and As resulted in a decrease in the 0.01 M Ca(NO(3))(2)-extractable concentrations of Cd and Zn. Shoot Cd and Zn concentration in Calamagrostis epigejos, the dominant plant species, also decreased in the presence of TBS. The addition of TBS and HA reduced sediment ecotoxicity and improved the growth of the total bacterial population. Hydroxylapatite improved plant species richness and diversity and decreased antioxidant enzymes in C. Epigejos and Urtica dïoica. Collembolan communities did not differ in abundance and diversity between the different treatments

Fate of cadmium in the rhizosphere of Arabidopsis halleri grown in a contaminated dredged sediment

International audienceIn regions impacted by mining and smelting activities, dredged sediments are often contaminated with metals. Phytotechnologies could be used for their management, but more knowledge on the speciation of metals in the sediment and on their fate after colonization by plant roots is needed. This work was focused on a Zn, Cd-contaminated contaminated dredged sediment from the Scarpe river (North of France). Zn, Cd hyperaccumulating plants Arabidopsis halleri from metallicolous and non metallicolous origin were grown on the sediment for five months in a pot experiment. The nature and extent of the modifications in Cd speciation with or without plant were determined by electron microscopy, micro X-ray fluorescence and bulk and micro X-ray absorption spectroscopy. In addition, changes in Cd exchangeable and bioavailable pools were evaluated, and Cd content in leachates was measured. Finally, Cd plant uptake and plant growth parameters were monitored. In the original sediment, Cd was present as a mixed Zn, Cd, Fe sulfide. After five months, although pots still contained reduced sulfur, Cd-bearing sulfides were totally oxidized in vegetated pots, whereas a minor fraction (8%) was still present in non vegetated ones. Secondary species included Cd bound to O-containing groups of organic matter and Cd phosphates. Cd exchangeability and bioavailability were relatively low and did not increase during changes in Cd speciation, suggesting that Cd released by sulfide oxidation was readily taken up with strong interactions with organic matter and phosphate ligands. Thus, the composition of the sediment, the oxic conditions and the rhizospheric activity (regardless of the plant origin) created favourable conditions for Cd stabilization. However, it should be kept in mind that returning to anoxic conditions may change Cd speciation, so the species formed cannot be considered as stable on the long term

Is phytoextraction a suitable green treatment for metal-contaminated sediments ?

International audienceThe cleaning of waterways by regular dredging generates great volumes of sediments and, owing to human activities, these sediments often contain large amounts of metals. These materials are usually spread on landfill sites. Phytoremediation could be a stategy for the reclamation of these polluted sediments. To our knowledge, phytoextraction with hyperaccumulating plants has been few tested on contaminated sediment. This work focuses on the mechanisms of Cd accumulation in Arabidopsis halleri, a Cd and Zn hyperaccumulator, and the effects of this species on a metal polluted sediment

High quality phased assembly of grape genome offer new opportunities in chimera detection

In perennial plants and especially those propagated through cuttings, several genotypes can coexist in a single individual, thus leading to chimeras. When the variant induces a noticeable phenotype modification, it can lead to a new cultivar. Viticulture already took economic advantage of this natural phenomenon: for instance, the berry skin of ‘Pinot gris’ derived from ‘Pinot noir’ by the selection of a chimera. Chimeras could also impact other crucial traits without being visually identified. Periclinal chimera where the variant has entirely colonized a cell layer is the most stable and can be propagated through cuttings. In grapevine, two functional cell layers are present in leaves, L1 and L2. However, lateral roots are formed from the L2 cell layer only. Thus, comparing DNA sequences of roots and leaves could allow chimera detection. In this study we used new generation Hifi long reads sequencing and recent bioinformatics tools applied to ‘Merlot’ to detect periclinal chimeras. Sequencing of ‘Magdeleine Noire des Charentes’ and ‘Cabernet franc’, the parents of ‘Merlot’, allowed haplotype resolved assembly. Pseudomolecules were built with few contigs, in some occasions only one per chromosome. This high resolution allowed haplotype comparison. Annotation from PN40024 was transferred to all pseudomolecules. Through variant detection, periclinal chimeras were found on both haplotypes. These results open new perspectives on chimera detection, which is an important resource to improve cultivars through clonal selection or breed new ones. Detailed results will be presented and discussed

Findings from the PP-SESAME experiment on board the Philae/ROSETTA lander on the surface of comet 67P

International audienceThe Permittivity Probe (PP-SESAME [1]) on-board the Philae Lander of the ROSETTA mission was designed to constrain the complex permittivity of the first 2 meters of the nucleus of comet 67P/Churyumov-Gerasimenko and to monitor its variations with time. Doing so, it is meant to provide unique insight into the composition (and activity if data could have been acquired longer) of the comet. In this paper, we present the analysis of the PP-SESAME measurements acquired during the first science sequence, on November 13, 2014, on the surface of the comet