Responses of hydrophilic lichens to global warming: preliminary results

International audienceLichens are among the most conspicuous and ubiquitous symbioses on the planet. They are highly adapted to terrestrial habitats of all climatic zones including the most hostile environments on Earth, such as high altitudes in the Himalayas or the cold deserts of Antarctica. Lichen is an association between fungus (mycobiont) and photosynthetic microorganisms (photobionts: cyanobacteria and/or microalgae). However a third symbiot is now considered: bacteria (bacteriobionts) living on and in lichen. Thus, the complex interactions between the metabolic pathways of each symbiotic partner are supposed to be necessary to keep safe the holobiont functioning in this wide range of environmental conditions. Microorganisms play here key metabolic roles e.g. photobionts mainly provide primary metabolites to mycobiont that is unable to synthesize or feed, whereas bacteriobionts may limit holobiont pathogens and grazers through antibiotics. However, considering the hot topic of global warming, the involvement of epithallic bacterial communities from inland aquatic environments in autoecological-disturbance regulation (e.g. thermic and osmotic stress) remains still unknown and needs deep investigations. The chemical interactions between symbiot biodiversity and their effects on host metabolome, need to be investigated. It is also necessary to focus on the involvement of bacterial metabolites in holobiont protection toward autoecological stress, and to highlight the benefits of their environmental release to photobiont-cell integrity and mycobiont homeostasis