Higher yields of cyclodepsipetides from Scopulariopsis brevicaulis by random mutagenesis

The ascomycete Scopulariopsis brevicaulis, which was isolated from the marine sponge Tethya aurantium, produces two cyclodepsipeptides, scopularides A and B [1]. Both peptides exhibit activity against several tumor cell lines. Within the EU-project MARINE FUNGI (EU FP7, 265926) one of our aims is to enhance the production of these secondary metabolites. We are in the process to establish two ways of random mutagenesis by both UV radiation and transposon-mediated. To this end we created UV-mutants and a miniaturised screening method was developed. UV-radiation was performed at 312 nm and the survival rate was set to 1 \%. With this method a mutant library was established. To screen these mutants for higher secondary metabolites production, we developed a miniaturised screening method which includes decreased cultivation volume, fast extraction and an optimised LC-MS analysis format. Using the UV mutagenesis, we were able to identify several mutants with a higher scopularide production in comparison to the wild type. One of these mutants, which produces three times more biomass and more than double the amount of scopularide A, has been used for another round of mutation. Next generation sequencing is being employed to identify the molecular genetic basis of the observed mutations. In parallel we employ transposable elements to introduce mutants [2]. The impact of transposons on gene expression as well as their ability to cause major mutations within the genome or single genes makes them an interesting tool for random mutagenesis [3, 4, 5]. We employ the Vader transposon in its homologous host and found that Vader mostly integrates within or very close to genes. Thus it appears to be a useful tool for transposon-mediated mutagenesis in A. niger (6). At current we try to enhance its usability by modifying the Vader element.