Gene

Function (biology)

Paleontology

Microorganism

Polyketide synthase

Polyketide

Aspergillus

Context (archaeology)

Natural product

Fungus

Aspergillus fumigatus

Streptomyces

Gene cluster

Bacteria

Genetics

Biosynthesis

Biochemistry

Botany

Computational biology

Biology

Microbiology

eLife

Microorganisms produce numerous secondary metabolites (SMs) with various biological activities. Many of their encoding gene clusters are silent under standard laboratory conditions because for their activation they need the ecological context, such as the presence of other microorganisms. The true ecological function of most SMs remains obscure, but understanding of both the activation of silent gene clusters and the ecological function of the produced compounds is of importance to reveal functional interactions in microbiomes. Here, we report the identification of an as-yet uncharacterized silent gene cluster of the fungus Aspergillus fumigatus, which is activated by the bacterium Streptomyces rapamycinicus during the bacterial-fungal interaction. The resulting natural product is the novel fungal metabolite fumigermin, the biosynthesis of which requires the polyketide synthase FgnA. Fumigermin inhibits germination of spores of the inducing S. rapamycinicus, and thus helps the fungus to defend resources in the shared habitat against a bacterial competitor.

Targeted induction of a silent fungal gene cluster encoding the bacteria-specific germination inhibitor fumigermin