scholarly journals Secretion of Iron(III)-Reducing Metabolites during Protein Acquisition by the Ectomycorrhizal Fungus Paxillus involutus

2020 ◽  
Vol 9 (1) ◽  
pp. 35
Author(s):  
Firoz Shah ◽  
Markus Gressler ◽  
Susan Nehzati ◽  
Michiel Op De Beeck ◽  
Luigi Gentile ◽  
...  
Keyword(s):  
Fenton Reaction ◽  
Ectomycorrhizal Fungus ◽  
Paxillus Involutus ◽  
Environmental Cues ◽  
Rapid Reduction ◽  
Fenton Chemistry ◽  
X Ray ◽  
Solid Iron ◽  
X Ray Absorption ◽  
Step Mechanism

The ectomycorrhizal fungus Paxillus involutus decomposes proteins using a two-step mechanism, including oxidation and proteolysis. Oxidation involves the action of extracellular hydroxyl radicals (•OH) generated by the Fenton reaction. This reaction requires the presence of iron(II). Here, we monitored the speciation of extracellular iron and the secretion of iron(III)-reducing metabolites during the decomposition of proteins by P. involutus. X-ray absorption spectroscopy showed that extracellular iron was mainly present as solid iron(III) phosphates and oxides. Within 1 to 2 days, these compounds were reductively dissolved, and iron(II) complexes were formed, which remained in the medium throughout the incubation. HPLC and mass spectrometry detected five extracellular iron(III)-reducing metabolites. Four of them were also secreted when the fungus grew on a medium containing ammonium as the sole nitrogen source. NMR identified the unique iron(III)-reductant as the diarylcyclopentenone involutin. Involutin was produced from day 2, just before the elevated •OH production, preceding the oxidation of BSA. The other, not yet fully characterized iron(III)-reductants likely participate in the rapid reduction and dissolution of solid iron(III) complexes observed on day one. The production of these metabolites is induced by other environmental cues than for involutin, suggesting that they play a role beyond the Fenton chemistry associated with protein oxidation.

Formation de Weddellite (CaC2O4∙2H2O) extracellulaire en culture in vitro par Paxillus involutus; signification de cette production pour la symbiose ecto- mycorhizienne

1984 ◽  
Vol 62 (6) ◽  
pp. 1116-1121 ◽  
Author(s):  
F. Lapeyrie ◽  
Monique Perrin ◽  
R. Pepin ◽  
G. Bruchet
Keyword(s):  
Calcium Oxalate ◽  
Culture Medium ◽  
Calcium Content ◽  
Ectomycorrhizal Fungus ◽  
Paxillus Involutus ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Calcium ◽  
Scanning Electron

Several forms of extracellular crystals have been observed in vitro on a semisynthetic culture medium. The conditions for their formation have not been determined. Their morphology and their localisation on the hyphal surface and in the culture medium have been investigated by means of scanning electron microscopy. These crystals have been identified as dehydrated calcium oxalate (Weddellite) using x-ray diffraction methods. Their high calcium content has been demonstrated with the scanning electron microprobe, by detecting the x-ray emission of calcium. The significance of calcium oxalate production by an ectomycorrhizal fungus is discussed.

scholarly journals Identification of jarosite and other major mineral Fe phases in acidic environments affected by mining-metallurgy using X-ray Absorption Spectroscopy: With special emphasis on the August 2014 Cananea acid spill

2019 ◽  
Vol 36 (2) ◽  
pp. 229-241 ◽  
Author(s):  
Ingrid Nayeli Escobar-Quiroz ◽  
Mario Villalobos-Peñalosa ◽  
Teresa Pi-Puig ◽  
Francisco Martín Romero ◽  
Javier Aguilar-Carrillo de Albornoz
Keyword(s):  
Absorption Spectroscopy ◽  
Copper Ions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selective Sequential Extraction ◽  
Metallurgical Wastes ◽  
Solid Iron ◽  
Oxide Phases ◽  
Mine Acid ◽  
X Ray Absorption

The sulfuric acid spill into the Sonora river, enriched in iron and copper ions from the Buenavista del Cobre mine (Cananea), gave way to the formation of various solid iron (Fe) phases. In this study, the mineral phases were identified by X-ray Absorption Spectroscopy (XAS) and bulk powder X-Ray Diffraction (XRD), and chemically through acid digestions for multielemental quantification, as well as a 3-step selective sequential extraction (SSE) to quantify the types of Fe oxide phases and the contribution of the associated elements. Jarosite was the only Fe mineral identified by XRD, but XAS allowed identification of jarosite with potentially toxic elements (PTEs) incorporated in its structure, making these elements less prone to leaching. In addition, very poorly crystalline phases such as schwertmannite and ferrihydrite were identified in several samples through XAS, which was confirmed by SSE. These phases are probably associated with PTEs. Other possible adsorbent Fe(III) minerals were also identified by XAS, such as maghemite and goethite; as well as mixed Fe(II)-Fe(III) minerals, such as green rust. It was possible to infer the influence of the acid spill on the different sampled areas through various Fe phases identified and/or the presence of gypsum. The influence was detected to be lower where the mineralogy was not associated to low pH and high sulfate concentrations. All precipitated Fe(III) phases downriver from the acid spill are known for their high retention capacities of PTEs either from incorporation into their structures and/or from surface adsorption, thus, contributing to the immobilization of the initial metal(loid) pollution caused by the acid spill. In addition, several other samples of mining-metallurgical wastes were analyzed by the same three techniques, suggesting many of the findings from the secondary Fe mineralogy of the Buenavista del Cobre mine acid spill as common processes occurring in mining-affected environments.

scholarly journals Involutin Is an Fe3+Reductant Secreted by the Ectomycorrhizal Fungus Paxillus involutus during Fenton-Based Decomposition of Organic Matter

2015 ◽  
Vol 81 (24) ◽  
pp. 8427-8433 ◽  
Author(s):  
Firoz Shah ◽  
Daniel Schwenk ◽  
César Nicolás ◽  
Per Persson ◽  
Dirk Hoffmeister ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ectomycorrhizal Fungi ◽  
Brown Rot ◽  
Ectomycorrhizal Fungus ◽  
Organic Matter Decomposition ◽  
Mineral Nutrient ◽  
Paxillus Involutus ◽  
Fenton Chemistry ◽  
Content Type

ABSTRACTEctomycorrhizal fungi play a key role in mobilizing nutrients embedded in recalcitrant organic matter complexes, thereby increasing nutrient accessibility to the host plant. Recent studies have shown that during the assimilation of nutrients, the ectomycorrhizal fungusPaxillus involutusdecomposes organic matter using an oxidative mechanism involving Fenton chemistry (Fe2++ H2O2+ H+→ Fe3++ ˙OH + H2O), similar to that of brown rot wood-decaying fungi. In such fungi, secreted metabolites are one of the components that drive one-electron reductions of Fe3+and O2, generating Fenton chemistry reagents. Here we investigated whether such a mechanism is also implemented byP. involutusduring organic matter decomposition. Activity-guided purification was performed to isolate the Fe3+-reducing principle secreted byP. involutusduring growth on a maize compost extract. The Fe3+-reducing activity correlated with the presence of one compound. Mass spectrometry and nuclear magnetic resonance (NMR) identified this compound as the diarylcyclopentenone involutin. A major part of the involutin produced byP. involutusduring organic matter decomposition was secreted into the medium, and the metabolite was not detected when the fungus was grown on a mineral nutrient medium. We also demonstrated that in the presence of H2O2, involutin has the capacity to drive anin vitroFenton reaction via Fe3+reduction. Our results show that the mechanism for the reduction of Fe3+and the generation of hydroxyl radicals via Fenton chemistry by ectomycorrhizal fungi during organic matter decomposition is similar to that employed by the evolutionarily related brown rot saprotrophs during wood decay.

X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

1978 ◽  
Vol 36 (1) ◽  
pp. 540-541
Author(s):  
G. Cliff ◽  
M.J. Nasir ◽  
G.W. Lorimer ◽  
N. Ridley
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Fraction ◽  
Present Series ◽  
Constant Independent ◽  
X Ray ◽  
Transmission Electron ◽  
Series Of Experiments ◽  
Image Position ◽  
X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

Use of SEM, X-ray analysis and TEM to localize Fe3+ reduction in roots

1988 ◽  
Vol 46 ◽  
pp. 392-393 ◽  
Author(s):  
William P. Wergin ◽  
P. F. Bell ◽  
Rufus L. Chaney
Keyword(s):  
Electron Microscopy ◽  
Root Hairs ◽  
Rapid Reduction ◽  
X Ray ◽  
Physical Evidence ◽  
Transmission Electron ◽  
Young Root ◽  
Insoluble Precipitate ◽  
Uptake And Transport ◽  
Scanning Electron

In dicotyledons, Fe3+ must be reduced to Fe2+ before uptake and transport of this essential macronutrient can occur. Ambler et al demonstrated that reduction along the root could be observed by the formation of a stain, Prussian blue (PB), Fe4 [Fe(CN)6]3 n H2O (where n = 14-16). This stain, which is an insoluble precipitate, forms at the reduction site when the nutrient solution contains Fe3+ and ferricyanide. In 1972, Chaney et al proposed a model which suggested that the Fe3+ reduction site occurred outside the cell membrane; however, no physical evidence to support the model was presented at that time. A more recent study using the PB stain indicates that rapid reduction of Fe3+ occurs in a region of the root containing young root hairs. Furthermore the most pronounced activity occurs in plants that are deficient in Fe. To more precisely localize the site of Fe3+ reduction, scanning electron microscopy (SEM), x-ray analysis, and transmission electron microscopy (TEM) were utilized to examine the distribution of the PB precipitate that was induced to form in roots.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

point-Analysis Using the Extrapolation Method in the Analytical Electron microscope

1990 ◽  
Vol 48 (2) ◽  
pp. 430-431
Author(s):  
Zenji Horita ◽  
Ryuzo Nishimachi ◽  
Takeshi Sano ◽  
Minoru Nemoto
Keyword(s):  
Electron Microscope ◽  
Extrapolation Method ◽  
X Ray ◽  
Absorption Correction ◽  
Point Analysis ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Data Points ◽  
Identical Composition ◽  
X Ray Absorption

Absorption correction is often required in quantitative x-ray microanalysis of thin specimens using the analytical electron microscope. For such correction, it is convenient to use the extrapolation method[l] because the thickness, density and mass absorption coefficient are not necessary in the method. The characteristic x-ray intensities measured for the analysis are only requirement for the absorption correction. However, to achieve extrapolation, it is imperative to obtain data points more than two at different thicknesses in the identical composition. Thus, the method encounters difficulty in analyzing a region equivalent to beam size or the specimen with uniform thickness. The purpose of this study is to modify the method so that extrapolation becomes feasible in such limited conditions. Applicability of the new form is examined by using a standard sample and then it is applied to quantification of phases in a Ni-Al-W ternary alloy.The earlier equation for the extrapolation method was formulated based on the facts that the magnitude of x-ray absorption increases with increasing thickness and that the intensity of a characteristic x-ray exhibiting negligible absorption in the specimen is used as a measure of thickness.

Sign in / Sign up

Export Citation Format

Share Document