Community Matters: Stress Tolerance of Bacterial Strains in Synthetic Microbial Consortia for Space Applications

Kurzfassung

Understanding microbial survival under stress is essential for astrobiology, especially in the context of planetary protection and the operation of closed habitats like the International Space Station (ISS). Traditional microbiological assays often focus on single bacterial strains, limiting our understanding of microbial behavior in more complex, natural-like contexts. Synthetic bacterial communities, in contrast, provide an experimentally tractable yet ecologically relevant system to examine interspecies interactions and cooperative stress responses. These interactions can radically alter survival since cooperative or competitive mechanisms control individual strain physiology in ways not represented in single-species assays. Synthetic bacterial communities represent a group of selected microorganisms that can be used as standard references for the study of specific environments. These standardized microbial communities are composed of microorganisms that have been demonstrated to occur, for example, in the ISS or spacecraft assembly facilities, etc. We evaluated the stress tolerance of selected bacterial strains both individually and within a defined synthetic bacterial community under conditions relevant to spaceflight, including desiccation, X-ray-irradiation, and oxidative stress (hydrogen peroxide). The tested strains represent typical members of the spacecraft microbiome and include genera such as Bacillus, Pseudomonas, and Staphylococcus. Survival rates were quantified using colony-forming unit (CFU) counts and metabolic activity assays. The stress tolerance of the strains differed between individual exposure and within the community. The survival of some strains was enhanced within the community, suggesting the presence of protective interspecies interactions such as biofilm formation or shared stressresponse signaling. Conversely, other strains showed reduced viability within the community, Abstract_EANA2025-148 http://www.eana-net.eu/conferences/EANA2025/abstract_show.php?id=148 1 von 2 20.11.2025, 17:11potentially due to antagonism or competitive exclusion. These findings could have direct implications for long-duration human spaceflight and planetary protection protocols. Microbial communities in spacecraft environments may display enhanced survivability and stress resilience due to their interactive dynamics, posing challenges for sterilization and containment strategies. Employing synthetic bacterial community-based models can therefore improve our predictive capabilities regarding microbial behavior in space and support the evaluation of existing and development of more effective countermeasures. In conclusion, our results highlight the necessity of considering community-level interactions when evaluating bacterial stress tolerance. Bacterial synthetic communities offer a powerful approach to bridge the gap between reductionist and systems-level microbiology, providing insights critical for both Earth-based biotechnology and the expanding frontier of space exploration.