Community matters: stress tolerance and survival of Bacillus subtilis and Staphylococcus capitis in a synthetic space habitat consortium

Kurzfassung

Introduction: Conventional microbiological methods typically examine isolated bacterial species, which limits the insight into how microorganisms behave in more realistic, complex ecosystems. In contrast, synthetic bacterial consortia offer a practical and ecologically meaningful model for studying species interactions and responses to stress. These interspecies dynamics, both cooperative and competitive, can significantly influence the survival and physiology of individual species, revealing patterns that single-species tests often miss. Exploring microbial resilience under stress is vital for advancing space microbiology and ensuring the functionality of enclosed environments like the International Space Station (ISS) and in the future in spacecraft traveling to the Moon or Mars. Methods: To assess the stress tolerance of bacterial species within a consortium, a synthetic bacterial consortium was constructed using species representative of the spacecraft microbiome, including genera such as Bacillus, Pseudomonas, and Staphylococcus. The stress tolerance of Bacillus subtilis and Staphylococcus capitis was evaluated both individually and within the defined consortium under spaceflight-relevant conditions, including desiccation, X-ray irradiation, and hydrogen peroxide exposure. Survival rates were quantified by colony-forming unit (CFU) counts. Co-cultivation approaches were employed to assess biofilm formation and growth within the consortium. Consortium dynamics following stress exposure and cultivation were further investigated using 16S rRNA gene sequencing. Results: The stress tolerance of B. subtilis and S. capitis differed between individual exposure and consortium conditions. Hereby, the consortium context influenced stress responses in a stressor-specific manner. Co-cultivation experiments demonstrated observable growth in various combinations of consortium members, with differences in early-stage biofilm formation and CFU Frontiers in Microbiology 01 frontiersin.orgKr¨ amer et al. 10.3389/fmicb.2026.1869903 counts noted. Investigations of consortium dynamics revealed a statistically significant difference before and after incubation indicating that over time the consortium reaches a stabilized relative abundance profile. Discussion: Our findings underscore the importance of considering communitylevel interactions when evaluating bacterial stress tolerance. Synthetic bacterial consortia represent a valuable approach to bridging the gap between reductionist and systems-level microbiology, offering critical insights for both terrestrial biotechnology and the advancement of space exploration.