Characterisation of the taxonomic and functional diversity of bacterial communities isolated from heartwood and sapwood of decaying oak

PI : Sophie Mieszkin (UMR 1136 Interactions Arbres/Micro-organismes – IAM)

Co-applicants : Eric Gelhaye (UMR 1136 Interactions Arbres/Micro-organismes – IAM); Philippe Gérardin (EA 4370 Laboratoire d’Etudes et de Recherche sur le Matériau Bois – LERMAB)

Collaborations : Stéphane Dumarçay (EA 4370 Laboratoire d’Etudes et de Recherche sur le Matériau Bois – LERMAB)

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Context — Microorganisms are the main wood decomposers in forest ecosystems. Among them, fungi are the most studied and are capable of using various extracellular lignocellulolytic enzymes to degrade complex polymers. At the opposite, the role of bacterial communities during wood degradation was underestimated despite evidences of their strong involvement in these processes. Thus, in addition to the lack of knowledge regarding the functional potential of wood-inhabiting bacterial communities, the structuring role of the two main wood compartments named sapwood and heartwood on bacterial communities was, to our knowledge, never assessed. The main difference between these two compartments relies mainly in their wood extractives content, which are secondary metabolites potentially toxic toward microorganisms. The heartwood has the highest extractive concentrations while oak has the particularity to store some extractives known to inhibit microbial growth.

Objectives — To investigate how decaying oak (Quercus petraea) and its different compartments (heartwood versus sapwood) shape both the taxonomic and functional diversity of bacterial communities.

Approaches — Culture-dependent methods are used to explore the functional (selective media and metabolic assays) and taxonomic (Sanger sequencing) diversity of a bacterial collection obtained from 9-months old decaying-oak and considering the two distinct wood compartments: heartwood and sapwood. The effect of oak extractives obtained from heartwood on the kinetic growth of a selection of bacterial isolates is also assessed.

Expected results and impacts — This project will allow understanding how wood compartments, characterized by their chemical composition, shape the wood-inhabiting bacterial communities. Furthermore, the effect of oak extractives on bacterial physiology will permit to identify which groups of bacterial isolates are resistant or sensitive to these metabolites in order to understand which molecular mechanisms are involved in their detoxification.