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Orchestrating the Plant-Arbuscular Mycorrhizal Fungi-Bacteria Continuum: Cooperation Strategies, Community Assembly, and Functional Synergy by Shilong Duan -
Mercredi 30 septembre 2026 à 16h00 - Salle Océan (B.002) - Bâtiment de Serres - Croix du Sud - 1348 Louvain-la-Neuve -
The plant–arbuscular mycorrhizal (AM) fungi–bacteria continuum represents an integrated framework of cross-kingdom cooperation important for nutrient cycling and sustainable agriculture. However, the mechanisms governing metabolic cooperation, bacterial community assembly, and spatial organization within the AM fungal hyphosphere remain poorly understood. This thesis investigates how AM fungi regulate bacterial partners through resource-dependent metabolic interactions, strain-specific recruitment, and spatial organization across contrasting environmental contexts.
Using a controlled in vitro system, the interaction between the AM fungus Rhizophagus irregularis and the phosphate-solubilizing bacterium (PSB) Rahnella aquatilis was first examined. Transcriptomic analyses showed that phosphorus (P) availability strongly regulated their cooperation. Low inorganic P enhanced complementary carbon (C) metabolism and P acquisition pathways in both partners, strengthening reciprocal C–P interactions, whereas high P availability suppressed these cooperative responses.
The thesis then examined how intraspecific variation among AM fungal strains shapes hyphospheric bacterial communities in soils under long term organic and conventional farming. Different strains of R. irregularis generated distinct bacterial assemblages and functional potentials, particularly those associated with organic P mineralization and nodulating bacteria. These strain-dependent effects were stronger under organic management soil, demonstrating that AM fungal strain identity is an important ecological driver of bacterial community assembly.
Finally, a three-compartment microcosm revealed spatial differentiation of bacterial functional groups along AM fungal hyphal networks. PSB were enriched in the distal hyphosphere, where they were associated with localized organic P mineralization, whereas nitrogen-fixing bacteria were preferentially migrated toward legume roots and associated with enhanced nodulation. These patterns indicate that AM fungal hyphae can spatially organize functionally distinct bacterial groups, with stronger interactions occurring under organic management.
Together, this thesis demonstrates that the plant–AM fungus–bacterium continuum is dynamically regulated by nutrient availability, fungal genetic variation, and spatial organization. These findings provide a conceptual basis for developing context-adapted microbial strategies to improve nutrient cycling, reduce fertilizer dependency, and enhance agricultural sustainability.
Jury members :
Prof. Stéphane DECLERCK (UCLouvain) (Supervisor)
Prof. Marnik VANCLOOSTER (UCLouvain) (Chairperson)
Prof. Annika GILLIS (UCLouvain) (Secretary)
Prof. Lin ZHANG (China Agricultural University, China)
Dr. Maryline CALONNE-SALMON (UCLouvain)
Prof. Marc ONGENA (ULiège)
Pay attention : the public defense of Shilong Duan will also take place in the form of a videoconference (Meeting ID : 314 715 769 419 174 - Password:
Rq7sf7Kd)
