Natural products from fungi associated with Macrotermitine termites and analysis of their genomic and biochemical origin

Fungus farming termites grow Termitomyces sp. fungi as their crop in underground chambers. Both partners mutually depend on each other: the insects provide optimal growth condition for their crop and the fungus serves as a food source for the termites that enables them to colonise otherwise inaccessible territory. Only if the symbiotic relationship is out of balance, other fungi than Termitomyces sp. (e.g. Pseudoxylaria sp.) are able to overgrow the mound. The aim of this thesis was to explore the natural product biosynthetic capacity of Termitomyces sp. and the respective metabolites as they could play a role in maintaining garden homeostasis by contributing to communication with symbiotic partners and by employing defensive activity against antagonistic fungi. Genome mining analysis revealed a conserved biosynthetic repertoire across Termitomyces sp. with terpene synthases as most abundant enzyme class with a great potential for detection of new enzyme activities and terpene metabolites. Furthermore, highly relevant terpene cyclases were expressed heterologously and tested for their activity which led among other things to the identification of a versatile bifunctional D-limonene/bisabolene synthase and an unusual terpene cyclase producing nectrianolin C and D. Some of the terpenes produced by the characterised enzymes were also identified as part of Termitomyces volatilome, which is highly dependent on the life stage of the fungus and differs from comb and soil volatiles. Identified volatiles are potenital signalling molecules in the termite mound to regulate fungal development, communication with termites and growth of antagonistic fungi. To investigate the interaction between the Termitomyces sp. and the stowaway-fungus found in termite mounds, new Pseudoxylaria strains were isolated within this thesis and investigated according to their biosynthetic potential to produce new natural products and their phylogenetic relationship in the family of Xylariaceae.