A next generation space antimicrobial: assessing microbial activity and reduction across the International Space Station

Abstract Microbial contamination in spacecraft poses a threat to crew health and operational integrity. Currently, microbial reduction aboard the International Space Station (ISS) relies on rigorous cleaning, which is time-consuming for astronauts. This study analyzes the ISS microbiome and applies a novel quaternized antimicrobial polymer coating to assess its effectiveness in mitigating microbial contamination and its durability over prolonged periods of interaction. The polymer was coated onto five material types representing common objects interacted with by the crew. Each material had six coupons placed on six placards in various ISS locations, while three placards remained on Earth to accumulate microbes from passive and direct transfer. The trial lasted six months, utilizing microbiological cell cultures and genomic analysis to assess bacterial communities and identify species. Among the six placards on the ISS, only one had sufficient viable bacteria to assess the polymers efficacy. On this placard, the polymer coating was shown to decrease culturable bacterial surface loads by 1.39 log10 (equal to a 95.9% reduction) compared with uncoated surfaces. Coated surfaces exhibited less genetic material and lower microbial species richness. Additionally, the polymer coating proved durable, persisting on ISS surfaces throughout the six-month period. This study demonstrates that the antimicrobial polymer coating can actively reduce microbial loads and remains on surfaces in zero gravity environments. Its application is likely beneficial when applied alongside other mitigation activities for viral and bacterial contamination, with potential uses in long-duration spaceflight to enhance crew health and maintain spacecraft integrity. We also generated data showing the lack of microbial presence on the ISS. Competing Interest Statement The authors have declared no competing interest. Footnotes This version of the manuscript has been revised to improve readability and descriptive improvements to the methodological experimental design, analysis, and statistical results. This has included a revision and additional statistical analysis and the inclusion of additional figures to support the results and discussion.