Enzyme secretion by ECM fungi and exploitation of mineral nutrients from soil organic matter.

Introduction Important nutrients in forest soils such as nitrogen and phosphorus are mostly recycled from natural polymeric compounds contained in litter and organic debris-for example nucleic acids, proteins, or chitin. Objectives Activities of enzymes such as phosphatases, proteases, cellulases, chitinases and laccase were shown in saprotrophic but also in ectomycorrhizal fungi and there is increasing evidence that these enzymes contribute not only to the functioning of the symbiosis but also to the mobilisation of nutrients. In the present review, we describe how enzyme secretion and localisation on fungal hyphae may be connected to the potential role in soil nutrient cycling. Results Recently developed methods for enzyme activity studies of ectomycorrhizae directly assayed in or collected from the field such as enzyme activity profiling and soil imprinting are described. Their value and limitations in different examples of ecological studies is highlighted and discussed also with respect to the role of other soil microorganisms associated with ectomycorrhizae. Conclusion The conclusion from our review is that enzyme activities of ECM and their associated microorganisms provide a potentially enormous plasticity of mycorrhizosphere functionality which is an open field for further research. Enzymes secretes par les champignons ectomycorhiziens et exploitation des elements mineraux contenus dans la matiere organique du sol