PEERS · Phycosphere Epibionts-mEdiated Resistance againSt fungi

Symbionts are essential components of healthy organisms, assuming functions often mediated by chemical communication. In aquatic environments, microbial primary producers such as phytoplankton possess complex epibiotic bacterial communities that contribute to their physiology by secretion of bioactive molecules. However, the role of symbiotic bacteria in mediating the host’s interaction with other coexisting microbes is poorly studied. PEERS’ aim is to unravel the key symbionts of phytoplankton mediating host interaction with zoosporic fungal parasites through the biosynthesis of antifungal compounds. Using a tripartite interaction model involving phytoplankton host, bacterial symbionts and fungal parasites, we will study (i) the diversity of bacteria associated with healthy and diseased host populations, and (ii) the symbionts’ biosynthesis of antifungal compounds. This study integrates molecular ecology, metabolomics, and bioactivity screenings coupled with advanced statistics and data processing methods. Aquatic microbial communities will be collected from the Baltic Sea during the secondment, where the phytoplankton-host and parasite interactions during fungal disease outbreaks are well documented. PEERS will address a fundamental ecological question about the role of symbiotic bacteria in driving host-fungal parasite interaction in the aquatic environment, providing critical knowledge for understanding future variations in aquatic biomes under current environmental changes. Additionally, it provides a perfect model system to discover antifungal chemical signals with industrial applications. PEERS offers cutting-edge training opportunities to generate results at the forefront of innovation in aquatic ecology and biotechnology. Moreover, it offers transdisciplinary networking possibilities supporting a One Health research approach, with significant impact on my career progression.