Discovery of novel secondary metabolites in Aspergillus aculeatus

Polyketides (PKs) and non-ribosomal peptides (NRPs) constitute large classes of diverse secondary metabolites (SMs) and are important sources for pharmaceuticals due to their structural diversity and wide variety of biological activities. Our investigation of the chemical profile of the industrially important black Aspergillus Aspergillus aculeatus by UHPLC-DAD-HRMS has identified several SMs already known from this organism. However, several compounds could not be unambiguously dereplicated wherefore some have been selected, purified and structure elucidated by 1D and 2D NMR spectroscopy, whereby several novel secondary metabolites have been discovered.
A. aculeatus has recently been genome-sequenced; however no genetic approaches have so far been described to facilitate genetic engineering. We here present a system for non-integrated (AMA1-based) gene expression in A. aculeatus based on the USERTM cloning technique. The AMA-1 based gene expression has successfully been applied to express genes in A. aculeatus and by this approach the function of a PKS gene has been established. Furthermore the technique was used to activate a silent cluster by expression of a transcription factor, leading to the production of two previously unknown compounds, which we propose to be of meroterpenoid origin.