Exocellular oxidases can be sensitive and selective biomarkers of fungal exposure to metals
2007
Lebrun, Jeremie | Lamy, Isabelle | Mougin, Christian
Background: Biological methods based on enzymatic activity measurements mayoffer promising perspectives for ecotoxicological risk assessment in soilscontaminated by heavy metals. Because of their ecological pertinence, we retainfilamentous fungi as models for the development of enzymatic methods.Aims: The present study aims to assess both selectivity and sensitivity of theresponse of exocellular oxidases secreted by the basidiomycete Trametesversicolor exposed to metals.Methods: We spiked with high amounts of metals pure cultures performed in liquidmedia to assess the selectivity of the enzymatic response. We used mediaexhibiting several levels of metal complexation to measure its sensitivity.Results: Laccase and manganese-peroxidase activities were highly stimulated inthe presence of copper, mercury and cadmium. By contrast, lead and zinc werewithout significant effects on these activities. Lignin-peroxidase activity was notmeasured in the control cultures, but it was strongly increased after fungalexposure to copper. Assays performed with mixtures of metals, reflecting soilmultiple contaminations, provided contrasted results. Then, culture mediaexhibiting low complexing properties led to an increased bioavailability of metals.As a consequence, we were able to measure the enzymatic responses atenvironmental levels of contaminants.Conclusion: Our results validate our hypothesis and allow us to develop studies insoils. We will now introduce Trametes versicolor in contaminated soils andmeasure the resulting enzymatic activities.
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