HYPHOBIOME

In recent times, the paradigm of a healthy organism has shifted from one that would be free of microbes to the realization of the ineluctable interdependence between any animal or plant and the microorganisms they host. This insight has prompted the development of new treatments in the fields of medicine and agronomy to promote host health. Naturally, studies have initially focused on hosts that are closest to us such as animals and plants. As it becomes increasingly clear that no complex organism is devoid of symbiotic associations, the remaining realms of the living are yet to be thoroughly explored. Fungi are amongst the most inconspicuous organisms of most soil ecosystems with regard to their relative abundance. They are still widely approached as independent organisms, just as animals and plants were not so long ago. While it is accepted that this might be a misconception, the extend of fungal interactions with other microorganisms is still largely unknown. In most terrestrial environments, bacteria and fungi cohabit and the interactions between both parties are widespread. They range from a distant exchange of molecules to a more specialized form of interaction based on direct physical contact. Some bacteria colonize the fungis hyphae surfaces while others can establish subpopulations within fungal cells. Albeit this type of association has been well described for selected fungi of the Mucoromycota, Glomeromycota, Ascomycota and Basidiomycota divisions, there is still substantial knowledge to be gained on the mechanisms underlying fungi-bacteria interactions. Furthermore, chances are high that the known diversity of fungi-bacteria associations is only the tip of the iceberg. The HYPHOBIOME project proposes to lay the path towards a better understanding of fungi-bacteria associations by focusing on a model of choice that will be subjected to an in-depth characterization. Preliminary observations on that model give us reason to believe that fungi host a diversity of specialized bacteria that have the ability to enter and live inside fungal cells. The chosen fungus is itself involved in associations with plants, which enables the study of tripartite interactions. Using a panel of descriptive approaches, we will identify the bacterial symbionts as well as their functions and activities within the fungal hyphae. This will be carried out on strains of a single fungal species isolated from various regions in Europe. We will further investigate the importance of bacterial symbionts to the fungal cell by studying the impact of their presence and absence on the fungis metabolism. Finally, the impact of the bacterial-fungal association on fungus-plant interaction will be determined.