Establishing and Characterizing of a synthetic ISS bacterial community for spaceflight applications: Stress responses and countermeasure

Abstract

Microbial contaminations are unavoidable consequences of human presence on crewed space missions. Microorganisms have been recovered from spacecrafts, most notably on board the International Space Station (ISS) and even from the surface of the Mars-Odyssey-Orbiter prior its flight to Mars. Although most of these microorganisms pose little risk to humans and hardware, some threaten crew health and the spacecraft integrity. To date, stress-response studies have largely focused on individual strains, yet in nature microorganisms exist as interacting communities. To address this, a synthetic ISS-related consortium of seven bacterial strains drawn from the genera most frequently isolated on the ISS was assembled. The synthetic ISS-related community was then subjected to various stress tests to analyze cell viability and stress response under simulated space conditions including desiccation, X-ray irradiation, and contact-killing on copper coated surfaces as a potential countermeasure. After community exposure, Bacillus subtilis and Staphylococcus capitis were selectively isolated based on their distinct antibiotic resistances to compare cell viability of the single strains versus them being part of the community. Under desiccation conditions, B. subtilis survival declined within the community whereas S. capitis survival displayed enhanced persistence. No marked difference emerged during X-ray irradiation. In contrast, both strains showed significantly reduced viability when exposed to copper coated surfaces within the community, with the most pronounced cell lethality observed after exposure to 100 at.% Cu surfaces. The results obtained do not reveal a clear trend regarding stress resistance that could be attributed to the bacterial community. Further investigations are therefore necessary to analyze survival strategies under extreme conditions and community interactions in more detail.