Marine fungi from sponges : biodiversity, chemodiversity and biotechnological applications

Marine environment represents an untapped source of fungal diversity, where it has been estimated that about 10% of fungi have been explored until now. Due to the lack of knowledge on marine fungi and their incredible biotechnological potential, this Ph.D. thesis focuses on a highly promising group of fungi: those associated with marine sponges. These fungi are both characterized by high biodiversity and chemodiversity, being the most successful producers of new bioactive molecules. On these premises, the main goal of the research was to cover the firsts and fundamentals aspects of the natural products discovery pipeline: from the isolation and identification of fungi from sponges to the isolation of molecules and the evaluation of their biological activity. This resulted in a multidisciplinary Ph.D. project that enclosed mycology, chemistry, biochemistry and biotechnology. In a “funnel-like” perspective, using multidisciplinary experimental approaches three main parts were developed: - The first aim was to isolate the fungal communities associated with sponges using several isolation techniques to increase the number of cultivable fungi. Four and three sponges were respectively collected in the Atlantic Ocean and in the Mediterranean Sea. Overall, 129 taxa were obtained; thanks to a polyphasic approach based on morphological, molecular and phylogenetic techniques, 84.5% of them were identified at the species level. Two fungal species Thelebolus balaustiformis and Thelebolus spongiae were here first described, updating the knowledge on marine fungal diversity. This work underlined the specificity of the fungal community for each sponge, leading to think that these animals are able to recruit their own mycobiota. - The second part was based on the investigation of the chemical diversity of marine fungi associated with the sponge Grantia compressa, using the OSMAC approach (One Strain – Many Compounds). Not surprisingly, it has been difficult to define a condition that promotes both the development of the mycelium and the secondary metabolites production for all fungi; generally, rich nutrients media are the best candidates to achieve the above-mentioned results. Among the tested fungi, Eurotium chevalieri MUT 2316 produce more metabolites than any other fungus and ten pure compounds were isolated. - The third part of this Ph.D. project aimed to test the biological activity of the ten fungal molecules. Two main research fields, pharmaceutical and environmental, were chosen as potential targets. Six compounds showed antibacterial activity, with isodihydroauroglaucin active against most of the Grampositive bacteria tested also with bactericidal activity. Dihydroauroglaucin and physcion were able to completely inhibit the replication of Influenza A virus, while neoechinulin completely inhibited Herpes Simplex Virus 1. Finally, the last series of bioassays aimed to face the urgent need of environmentally friendly antifouling and highlighted several molecules already active at extremely low concentrations, inhibiting the adhesion and growth of both bacteria and microalgae. As result, a mix of few compounds produced by E. chevalieri MUT 2316 would inhibit all the bacteria and microalgae tested. In conclusion, this Ph.D. project highlighted the outstanding biodiversity and chemodiveristy of marine fungi inhabiting sponges. The molecules isolated from E. chevalieri MUT 2316 found applications in different research fields and represent promising candidates for the development of new drugs and antifouling paints.