Fate of lignin altered by Brown Rot And White rOt fungi

PI : Delphine Derrien (UMR 1443 Bureau d’Economie Théorique Appliquée – BETA)

Co-applicants : Eric Gelhaye (UMR 1136 Interactions Arbres/Micro-organismes – IAM)

Collaborations : Matthieu Barrandon (IECL- Institut Elie Cartan de Lorraine, Université de Lorraine, Nancy), Barry Goodell (Department of Microbiology, University
 of Massachusetts, USA), Gry Alfredsen (NIBIO – Norwegian Institute of Bioeconomy Research, Norway)

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Context — In forest ecosystems, the wood rotting Basidiomycota fungi play a central role in lignocellulose degradation. They are indeed the only microorganisms able to remove or circumvent the lignin barrier that hinders access to plant polysaccharides. White rot fungi degrade polysaccharides and lignin using enzymatic systems. Brown rot fungi employ a different strategy based on the production of hydroxyl radicals by a Fenton reaction. They decompose carbohydrate, but leave behind them a modified lignin considered to be resistant to degradation by other organisms.

Brown rot fungi have evolved from ancestral white rot in a process accompanied by the loss of some cellulases and of all lignin-modifying enzymes. It has been suggested, but not verified, that this evolution provided them an energetic advantage over the white rot fungi.

Objectives — We want to explore the relationships between the strategies developed by brown rot and white rot fungi and the chemical properties of the altered residues to better predict how long certain chemical components will persist in the soil.

Approaches — Wood substrates will be incubated either with brown rot or white rot fungi. Change in their biochemistry and enzyme production will be monitored to estimate the energy cost and gains associated with each decay pathway. The fate of the altered substrate generated by brown rot and white rot fungi will then be explored after burial in the soil. The experimental dataset will be used to calibrate a new model of carbon dynamics, based on microbe and enzymes traits.

Expected results and impacts — The project will enhance our fundamental knowledge of mechanisms involved in the degradation of woody litter. It will also contribute to the global effort for enhancing carbon sequestration in soil by assessing the potential of altered lignin for carbon sequestration and by developing an innovative microbial model of soil carbon dynamics.