Elucidation of the Biosynthesis of Rickiols

Abstract

Rickiols are a novel class of fungal macrolides with promising antibiotic properties, particularly against Gram-positive bacteria. Despite their structural elucidation in 2017, the genes responsible for their biosynthesis in the filamentous fungus Hypoxylon rickii remained unidentified. This thesis aims to elucidate the biosynthetic gene cluster (BGC) of Rickiols and functionally validate it via heterologous expression in Aspergillus oryzae, through molecular cloning and transformation. The genes encoding core enzymes, such as highly reducing polyketide synthase (hrPKS), thioesterase (TE); and genes encoding tailoring enzymes like cytochrome P450, short-chain dehydrogenase/reductase (SDR), and flavin-dependent monooxygenase (FMO), were introduced into A. oryzae using synthetic biology tools. The expression of these genes led to the successful production of several Rickiols. The presence and chemical structures of the new compounds was confirmed by HPLC-MS and NMR. These findings lay the groundwork for the future development of scalable microbial production systems that could be used to generate new antibiotics or chemical variants with enhanced therapeutic potential, avoiding the need for chemical synthesis