Effect of metal speciation on the functional and morphological responses of soil fungi: case of Cu and Zn in Trametes versicolor - INRAE - Institut national de recherche pour l’agriculture, l’alimentation et l’environnement Accéder directement au contenu
Poster De Conférence Année : 2008

Effect of metal speciation on the functional and morphological responses of soil fungi: case of Cu and Zn in Trametes versicolor

Résumé

Filamentous fungi are part of major biomass in soil and are key actors of soil functioning due to their ability to produce extracellular enzymes. It is known that metals can alter extracellular enzymatic activities as well as morphology in fungi. Thus fungal responses to metals were suggested to be used as biomarkers of metal exposure in soils. Such biomarkers are needed in the environmental risk assessment, to develop methods for measuring the impact of metal contamination on soil microorganisms. However it is not well known how the metal speciation, linked to the metal bioavailability, influences the soil fungi responses to the presence of metals thus limiting the predictive interest in such biomarkers. The present study aims at investigating both the morphological responses and the sensitivity and selectivity of extracellular oxidases produced by the filamentous fungus, Trametes versicolor, exposed to Cu or Zn, taking into account the speciation of these two metals. For that purpose, the activities of three peroxidases were used as biomarkers of exposure and of bioavailability: the laccase, manganese- and lignin-peroxidases. Activities were monitored from pure cultures performed in various liquid media exhibiting several levels of metal complexation in order to vary metal bioavailability. Total metal contents from 0.1 µM to 1 mM and three liquid media, either rich or poor in organic ligands, were tested. Morphological responses were characterized in scanning electron microscopy. Theoretical speciation of Cu and Zn was calculated using the SOILCHEM thermodynamic program at the initial stage, and an Ion Selective Electrode was used to determine the free copper contents in the various media. Our results showed that Zn had no effect on the three oxidases tested. Cu however highly stimulated laccase and manganese-peroxidase activities. Lignin peroxidase was not measured in the control cultures without metals, but was found specifically produced after fungal exposure to Cu. Culture media exhibiting low complexing properties led to an increase in intensity and sensitivity of oxidase responses, suggesting a higher metal bioavailability. Moreover experimental speciation of Cu showed that Cu2+ contents were higher in the low complexing media. Theoretical speciation showed that only a few percentage of total Cu and Zn were in the free forms, the other forms were complexes of Zn and Cu with the organic or inorganic ligands. In our conditions, we were able to measure enzymatic responses to Cu at environmental levels of contamination (1 µM). Only Zn was found to impact the morphology of fungi during exposure. This result contrasted with the fact that no significant stimulation of oxidase activity could be detected in our experimental conditions. Our results show that the response of fungi is specific of a metal and depends on metal speciation: oxidases are stimulated in the presence of copper but no impact could be found on fungi morphology, while Zn had an impact on fungi morphology but had no effect on oxidase activities. This specificity and sensitivity confirm that fungal responses can be useful tools for metal ecotoxicity assessment that need to be tested in contaminated soils.
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Dates et versions

hal-02824546 , version 1 (06-06-2020)

Identifiants

  • HAL Id : hal-02824546 , version 1
  • PRODINRA : 23679

Citer

Jérémie D. Lebrun, Albert Kollmann, Nelly Wolff, Isabelle Lamy, Christian Mougin. Effect of metal speciation on the functional and morphological responses of soil fungi: case of Cu and Zn in Trametes versicolor. 5. ISMOM International Symposium of Interactions of Soil Minerals with Organic Components and Microorganisms Commmission, Nov 2008, Pucon, Chile. J. Soil Sci. Plant Nutr., 8 (3), pp.272-273, 2008. ⟨hal-02824546⟩

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