Fungi are the most diverse organisms of the world and many different species form part of the normal human commensal microflora. The yeast Candida parapsilosis and Rhodotorula mucilaginosa are present in the human epidermis and can be opportunistic when immunocompromised scenarios are present. The tendency of yeast isolates to respond and adapt to environmental stress is associated with increased virulence such as resistance to antifungals, increased filamentation and increased fungal biofilm formation. The present research was designed to test the virulence related phenotypes of Candida parapsilosis and Rhodotorula mucilaginosa isolated from the International Space Station. Fungal commensals and fungal pathogens require a better understanding of the response to space conditions (such as radiation, microgravity, and depleted oxygen) for spaceflight crew safety. Viable cells were isolated and retrieved from the International Space Station, and they were compared to terrestrial controls. Isolates were observed for the virulence phenotypes: antifungal resistance, filamentation, and capsule formation. ISS isolates demonstrated an increased resistance to the antifungals Fluconazol, Amphotericin B, and Caspofungin, moreover, they demonstrated increased biofilm formation, filamentation and capsule formation
