Ectomycorrhizal fungi as drivers for iron-mediated oxidation of soil organic matter

Oxidative decomposition of soil organic matter (SOM) determines the fraction of carbon that is either stored or emitted into the atmosphere as CO2. Current models attribute this oxidation largely to the activity of extracellular enzymes.

However, recent studies suggest that non-enzymatic processes including the action of reactive oxygen (ROS) species generated by Fenton-like reactions at the surface of redox active iron containing minerals contribute significantly to oxidative decomposition of SOM. Organic and mineral soil layers of boreal forest are rich in iron oxides.

Ectomycorrhizal (ECM) fungi often dominate the microbial biomass in these environments.

The aim of this four-year project is to examine the capacity of ECM fungi of diverse ecologies and evolutionary histories to induce ROS and oxidize SOM associated with iron oxides.

We will examine the mechanisms by which these fungi produce ROS using laboratory-scale systems combined with isotopic, spectroscopic and chromatographic methods.

We will use experiments and dynamic modelling to determine the main environmental and biological regulators controlling the production of ROS.

This is an interdisciplinary project involving competences in microbial ecology, molecular geochemistry and systems biology.

If the capacity to induce Fenton-like reactions at mineral surfaces is widespread among ECM fungi, the role of these fungi in soil C cycling may be much more important than currently considered.