Elucidation of specific interaction between the model organism Aspergillus nidulans and Streptomycetes

Streptomycetes are soil-dwelling gram-positive bacteria. They are well-known producers of a multitude of secondary metabolites. Two species, Streptomyces rapamycinicus (NRRL 5491) and S. iranensis HM35 (DSM 41954) which exhibit a high similarity at the genomic level (1) are of special interest. Both strains are not only rapamycin producers (2) but also specifically induce the formation of secondary metabolites in filamentous fungi, e.g. in the important model fungus A. nidulans (3) and in the pathogenic fungus A. fumigatus (4). These interactions provide an excellent model system to elucidate the  underlying molecular mechanisms how a silent fungal secondary metabolism gene cluster can be activated by a bacterium. To identify the primary bacterial signal we generated a random Tnp(a) transposon insertion mutant library of S. iranensis. For this purpose, a modified pTNM transposon vector was used. In vivo expression of the codon usage optimized transposase gene tnp(a) and its random insertion into the S. coelicolor genome have been shown previously. Both the successful conjugation of pTNM_kan into S. iranensis as well as the generation of a S. iranensis mutant library was achieved. Currently, we verify the selective induction of the transposase gene expression by analyzing random transposon insertion mutants. First results of the mutant library screening directed to identify genes involved in the specific fungus-streptomycete interaction will be presented.

(1)   Hamedi et al. (2010). Int. J. Syst. Evol. Microbiol. 60:1504-1509

(2)   Horn et al., (2014). Genome Announc. 2(4):e00616-14.

(3)   Schroeckh et al. (2009). PNAS 106:14558-14563

(4)   König et al., (2013). ChemBioChem 14:938-942.