

We also propose that FwnA-mediated melanin production plays a role in A. niger’s adaptation to simulated microgravity, as deletion of Δ racA leads to changes in biofilm thickness, spore production and total biomass. We suggest that the Rho GTPase RacA might play a role in A. Results show that simulated microgravity affects colony growth in a strain-dependent manner, leading to thicker biofilms (vegetative mycelium) and increased spore production. niger colonies that reveal a complex ultrastructure and biofilm architecture, and provide insights into fungal colony development, both on ground and in simulated microgravity. Our study presents never before seen scanning electron microscopy (SEM) images of A. Three strains were included: a wild-type strain, a pigmentation mutant (Δ fwnA), and a hyperbranching mutant (Δ racA). niger colony growth on agar in normal gravity (Ground) and simulated microgravity (SMG) conditions by fast-clinorotation. Because fungal colonies grown on agar can be considered analogs for surface contamination, we investigated A. niger colony growth, in particular regarding the vegetative mycelium (biofilm) and spore production, will help prevent and control fungal contaminations in indoor habitats on Earth and in space. Aboard the ISS, microorganisms and astronauts are shielded from extreme temperatures and radiation, but are inevitably affected by spaceflight microgravity. Surface contamination relies on two key-features of the fungal colony: the fungal spores, and the vegetative mycelium, also known as biofilm. niger can ultimately impact human health and habitat safety. Being able to colonize and biodegrade a wide range of surfaces, A. The biotechnology- and medicine-relevant fungus Aspergillus niger is a common colonizer of indoor habitats such as the International Space Station (ISS). 3Robert Koch Institute, Advanced Light and Electron Microscopy (ZBS 4), Berlin, Germany.2Chair of Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany.1German Aerospace Center (DLR), Institute of Aerospace Medicine, Radiation Biology Department, Aerospace Microbiology Research Group, Cologne, Germany.Marta Cortesão 1,2*, Gudrun Holland 3, Tabea Schütze 2, Michael Laue 3, Ralf Moeller 1 and Vera Meyer 2†
