Addressing Fungal Contamination - Testing Antifungal Materials and Radiation-Driven Decontamination Methods

Abstract

Filamentous fungi such as Aspergillus and Penicillium sp. (also known as “mold”) represent some of the predominant contaminations found onboard the Mir (Russian space station) and the International Space Station (ISS). These filamentous fungi can release a wide range of organic volatile compounds and mycotoxins. They are also some of the most abundant human associated opportunistic pathogens, being responsible for over 3x10⁸ fungal infections worldwide. The presence of filamentous fungi in manned spaceflight missions can cause complex risks due to their fast growth, spore forming and dispersal, high tolerance to disinfectants and material degradation. As spores, they can spread and survive under extreme and seemingly sterile conditions, being a major cause for food spoilage. To monitor and control fungal dispersal and growth in spaceflight indoor settings and material contamination, the resistance of fungal spores towards spaceflight-relevant conditions needs to be explored and understood. The aim of this thesis was to test innovative decontamination methods to inactivate spores, and to test preventive measures of fungal spore distribution and growth. We have tested the resistance of fungal spores to low pressure plasma sterilization, UV-C and coppercontaining metal surfaces. Spores of Aspergillus niger with black pigmentation (melanized) were shown to be more resistant to low pressure plasma sterilization and UV-C irradiation than melanindeficient (less pigmented) mutant spores. This suggests that the pigmentation of a fungal spore acts as a photo protectant and enhances fungal spore resistance. In order to prevent spore dispersal and attachment, we tested different types of metal surfaces (e.g. with and without copper) and their effects on spore viability. Here, known antibacterial copper surfaces ions were seen to only slightly reduced fungal spore. Summarizing, this thesis demonstrates that fungal spores of A. niger are highly tolerant towards various decontamination parameters showing the urgent need for novel methods that can be applied to upcoming and space missions.