Growth and biofilm formation of Penicillium chrysogenum in simulated microgravity

Penicillium sp. are one of the main fungal genera detected on board the Russian Space Station (MIR) and the International Space Station (ISS), demonstrating its ability to grow on the space stations´ walls and to maintain growth under microgravity (1-3). As a spore-forming microorganism, Penicillium sp. poses a concern for planetary protection and to human/astronaut health, as its spores, associated with respiratory diseases, can be dispersed through the air (4). Fungal growth on the ISS has shown to promote biodegradation of the spacecraft materials, compromising their integrity. Biofilms are groups of organisms adhered to each other by self-synthesized extracellular polymeric substances, and are ubiquitous in industrial and natural environments (5). It has been reported that Penicillium sp. forms biofilms, which are associated with higher tolerance/resistance to adverse conditions (6). Therefore, biofilm formed on the ISS may have deleterious effects on astronaut’s health and/or on ISS materials. To gain valuable knowledge to control biofilm during long duration spaceflight missions, the NASA-funded project “Characterization of Biofilm Formation, Growth, and Gene Expression on Different Materials and Environmental Conditions in Microgravity” is currently being prepared. Pre-flight testing include: defining and optimizing the growth medium and culturing conditions of P. chrysogenum DSM 1075; characterizing the morphological response of P. chrysogenum growth under simulated microgravity; assessing biofilm formation by P. chrysogenum under different conditions. The study of this fungal strain represents the beginning of a new line of research on board ISS. The knowledge gained can be applicable to a) the safety and maintenance of crewed spacecraft, b) planetary protection, c) mitigation of biofilm-associated illnesses on the crew, as well as on the Earth. Besides, P. chrysogenum is of major medical and historical importance, as it presents the original and present-day industrial source of the antibiotic penicillin, and as an important producer of antifungal proteins and other relevant enzymes

Design of a spaceflight biofilm experiment

Biofilm growth has been observed in Soviet/Russian (Salyuts and Mir), American (Skylab), and International (ISS) Space Stations, sometimes jeopardizing key equipment like spacesuits, water recycling units, radiators, and navigation windows. Biofilm formation also increases the risk of human illnesses and therefore needs to be well understood to enable safe, long-duration, human space missions. Here, the design of a NASA-supported biofilm in space project is reported. This new project aims to characterize biofilm inside the International Space Station in a controlled fashion, assessing changes in mass, thickness, and morphology. The space-based experiment also aims at elucidating the biomechanical and transcriptomic mechanisms involved in the formation of a “column-and-canopy” biofilm architecture that has previously been observed in space. To search for potential solutions, different materials and surface topologies will be used as the substrata for microbial growth. The adhesion of bacteria to surfaces and therefore the initial biofilm formation is strongly governed by topographical surface features of about the bacterial scale. Thus, using Direct Laser-Interference Patterning, some material coupons will have surface patterns with periodicities equal, above or below the size of bacteria. Additionally, a novel lubricant-impregnated surface will be assessed for potential Earth and spaceflight anti-biofilm applications. This paper describes the current experiment design including microbial strains and substrata materials and nanotopographies being considered, constraints and limitations that arise from performing experiments in space, and the next steps needed to mature the design to be spaceflight-ready. Keywords: Bacteria; Fungi; Pseudomonas aeruginosa; Penicillium rubens; Direct laser-interference patterning (DLIP); Lubricant-impregnated surface (LIS)United States. National Aeronautics and Space Administration (Grant 80NSSC17K0036