Changes in chemical fractionation of copper and zinc in soil as a function of incubation moisture content and organic matter amendments.

Copper and zinc are essential micronutrients that are potentially toxic when present in excess in soils. Their bioavailability depends on their speciation in soil, but this may vary with environmental conditions. Aeration and hence redox conditions, and organic matter amendments are among the factors likely to cause variation on metal fractionation.

pH-Dependent Changes in Structural Stabilities of Bt Cry1Ac Toxin and Contrasting Model Proteins following Adsorption on Montmorillonite.

The environmental fate of insecticidal Cry proteins, including time-dependent conservation of biological properties, results from their structural stability in soils. The complex cascade of reactions involved in biological action requires Cry proteins to be in solution. However, the pH-dependent changes in conformational stability and the adsorption-desorption mechanisms of Cry protein on soil minerals remain unclear.

Arbuscular Mycorrhizal Fungi and Soil Quality Indicators in genotypes With Different Drought Tolerance Levels.

Silviculture has great importance worldwide, and the use of species, which account for 75% of the local planted forest in Brazil, is one of the factors that contributes to the success of this activity in the country. Despite its adaptability, the yield of is often affected by climate change, particularly water deficiency. Plants have developed strategies to mitigate water stress, for example, through their association with mycorrhizal fungi.

and P-NMR Study of the Phosphate Transport and Polyphosphate Metabolism in in Response to Plant Roots Signals.

We used and phosphorus-31 nuclear magnetic resonance (P-NMR) spectroscopy to follow the change in transport, compartmentation and metabolism of phosphate in the ectomycorrhizal fungus in response to root signals originating from host () or non-host () plants. A device was developed for the studies allowing the circulation of a continuously oxygenated mineral solution in an NMR tube containing the mycelia. The studies were performed on fungal material after several consecutive treatment steps (freezing in liquid nitrogen; crushing with perchloric acid; elimination of perchloric acid; freeze-drying; dissolution in an appropriate liquid medium).

Establishing a Symbiotic Interface between Cultured Ectomycorrhizal Fungi and Plants to Follow Fungal Phosphate Metabolism.

In ectomycorrhizal plants, the fungal cells colonize the roots of their host plant to create new organs called ectomycorrhizae. In these new organs, the fungal cells colonize the walls of the cortical cells, bathing in the same apoplasm as the plant cells in a space named the 'Hartig net', where exchanges between the two partners take place. Finally, the efficiency of ectomycorrhizal fungi to improve the phosphorus nutrition of their host plants will depend on the regulation of phosphate transfer from the fungal cells to plant cells in the Hartig net through as yet unknown mechanisms.

A Method for Radioactive Labelling of to Study Plant-fungus Interactions.

In order to quantify P accumulation and P efflux in the ectomycorrhizal basidiomycete fungus , we supplied P to mycelia previously grown in liquid medium. The culture had four main steps that are 1) growing the mycelium on complete medium with P, 2) transfer the mycelia into new culture solution with or without P, 3) adding a solution containing P and 4) rinsing the mycelia before incubation with or without plant. The main point is to rinse very carefully the mycelia after P supply in order to avoid overestimation of P efflux into the medium.

Fate of insecticidal Bacillus thuringiensis Cry protein in soil: differences between purified toxin and biopesticide formulation.

Background: Bacillus thuringiensis produces insecticidal proteins known as Cry, and its efficiency and absence of side effects make it the most widely used biopesticide. There is little information on the role of soils in the fate of Cry proteins from commercial biopesticide formulations, unlike toxins from genetically modified crops, which have been intensively studied in recent years. The persistence of Cry in soil was followed under field and laboratory conditions.

The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and P NMR spectroscopy study.

Ectomycorrhizal (ECM) association can improve plant phosphorus (P) nutrition. Polyphosphates (polyP) synthesized in distant fungal cells after P uptake may contribute to P supply from the fungus to the host plant if they are hydrolyzed to phosphate in ECM roots then transferred to the host plant when required. In this study, we addressed this hypothesis for the ECM fungus Hebeloma cylindrosporum grown in vitro and incubated without plant or with host (Pinus pinaster) and non-host (Zea mays) plants, using an experimental system simulating the symbiotic interface.

Adsorption of alexa-labeled Bt toxin on mica, glass, and hydrophobized glass: study by normal scanning confocal fluorescence.

We studied the kinetics of adsorption of alexa-labeled Bt toxin Cry1Aa, in monomer and oligomer states, on muscovite mica, acid-treated hydrophilic glass, and hydrophobized glass, in the configuration of laminar flow of solution in a slit. Normal confocal fluorescence through the liquid volume allows the visualization of the concentration in solution over the time of adsorption, in addition to the signal due to the adsorbed molecules at the interface. The solution signal is used as calibration for estimation of interfacial concentration.

Mycorrhizal association of maritime pine, Pinus pinaster, with Rhizopogon roseolus has contrasting effects on the uptake from soil and root-to-shoot transfer of 137Cs, 85Sr and 95mTc.

The beneficial role of mycorrhizal association on plant nutrition and water supply is well-known, however, very little information exists with respect to the availability of radionuclides. We have measured the effect of controlled mycorrhizal association on the root uptake from soil and accumulation in leaves of three radionuclides. The radionuclides have contrasting chemical and biological properties: Cs is strongly adsorbed on soil, has no biological role and is a close analogue of potassium; Sr is less strongly adsorbed on soil and behaves very similarly to calcium; and Tc is very mobile in soil as pertechnetate, but immobilised when reduced to Tc(IV), it is also considered to be easily assimilated by biological systems.

Adsorption and desorption of 85Sr and 137Cs on reference minerals, with and without inorganic and organic surface coatings.

The adsorption properties of reference minerals may be considerably modified by the presence of the inorganic and organic coatings that are ubiquitous in soils. It is therefore important to assess the effect of such coatings to evaluate the relevance of adsorption studies on pure minerals. The adsorption of trace amounts of (85)Sr and (137)Cs has been studied in dilute suspensions for various minerals that are common components of soils: quartz, calcium carbonate, kaolinite, montmorillonite and illite.

Fate of prions in soil: adsorption and extraction by electroelution of recombinant ovine prion protein from montmorillonite and natural soils.

Prions, the infectious agents thought to be responsible for transmissible spongiform encephalopathies, may contaminate soils and have been reported to persist there for years. We have studied the adsorption and desorption of a model recombinant prion protein on montmorillonite and natural soil samples in order to elucidate mechanisms of prion retention in soils. Clay minerals, such as montmorillonite, are known to be strong adsorbents for organic molecules, including proteins.

Evolution of Sr distribution coefficient as a function of time, incubation conditions and measurement technique.

A thorough understanding of the dynamics of radiostrontium in soil is required to allow accurate long-term predictions of its mobility. We have followed the soil solution distribution of 85Sr as a function of time under controlled conditions over 4 months and studied the effect of soil moisture content and organic matter amendments. Data have been compared to redox conditions and soil pH.