Designing and Optimizing a Biofilm Experiment for Space Flight

Thornhill, Starla G.
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The International Space Station (ISS) is a built environment that has been continuously inhabited since November 2000. Living with the crew are the microorganisms carried to the ISS as normal astronaut flora and by accidental introduction in supplies. Microorganisms have established biofilms in the water recovery system (WRS) that recycles urine to provide drinking water to the ISS crew. Biofilms in the WRS can serve as a reservoir for opportunistic pathogens, including Escherichia coli and Pseudomonas aeruginosa, and can also induce clogs and corrosion damage on stainless-steel components. To investigate biofilm formation, silver disinfection susceptibility, and potential microbial corrosion in space flight, an experiment will be launched to the ISS on SpaceX-21 in December 2020. To model biofouling in the WRS, mixed-species biofilms of E. coli and P. aeruginosa will be cultured in artificial urine on 316L grade stainless-steel using a specialized BioCell apparatus. Flight samples will be compared to simultaneously tested ground (full gravity) controls. This research describes the design and optimization of the flight experiment, BioCell, ground-based silver disinfection capability, and data collection and analysis pathways for post-flight corrosion analysis. Analysis of pre-flight experiments shows a differential response to long-term silver disinfection treatment and suggests that corrosion on stainless steel could be the result of electrochemical processes, which may be exacerbated by silver fluoride treatment. Characterizing the microbial response to silver disinfection in flight will allow for a better understanding of the growth and treatment of biofilms on ISS.
Biofilms, Space flight, Silver disinfection, Corrosion
Thornhill, S. G. (2020). <i>Designing and optimizing a biofilm experiment for space flight</i> (Unpublished dissertation). Texas State University, San Marcos, Texas.