Microbial Growth in an Enceladus Ocean Analog Medium Informed by Mineral Stability Modeling

Elkassas, S. M.; Ely, T.; Zhivkova, T.; Patterson, A.; Weeks, K.; Mitchell, S.; Hayes-Guastella, L.; Nathan, V.; Serres, M.; Shock, E.; Girguis, P.; German, C.; Klein, F.; Seewald, J.; Huber, J. A.

doi:10.64898/2026.06.29.735333

bioRxiv · 10.64898/2026.06.29.735333

Microbial Growth in an Enceladus Ocean Analog Medium Informed by Mineral Stability Modeling

Elkassas, S. M.·Ely, T.·Zhivkova, T.·Patterson, A.·Weeks, K.·Mitchell, S.·Hayes-Guastella, L.·Nathan, V.·Serres, M.·Shock, E.·Girguis, P.·German, C.·Klein, F.·Seewald, J.·Huber, J. A.

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Abstract

Evidence from the Cassini mission confirmed that Saturns moon Enceladus hosts a subsurface alkaline ocean where rock-water reactions may generate redox disequilibria capable of supporting microbial metabolisms. To investigate potential microbial survival under simulated Enceladus ocean conditions, we used thermodynamic modeling to develop a salt formulation consistent with one possible Enceladus ocean composition and supplemented it with putative microbial energy sources to create a growth medium. The medium was inoculated with samples from diverse ocean world analog environments on Earth to determine which microorganisms could persist under Enceladus-like conditions. The microorganisms persisting in this geochemically bounded medium were heterotrophic, metabolically versatile bacteria with low carbon requirements. Genomic and physiological analyses further showed the presence of multiple stress-response pathways, sodium-based bioenergetic systems, osmoregulation strategies, and other adaptations consistent with survival in alkaline, low-nutrient settings. These results suggest that some stress-tolerant heterotrophic bacteria may serve as useful model organisms for life in Enceladus subsurface ocean. These findings demonstrate the value of geochemically modeled media as a framework for constraining habitability, identifying relevant biosignatures, and probing potential microbial survival strategies beyond Earth.

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Elkassas, S. M., Ely, T., Zhivkova, T., Patterson, A., Weeks, K., Mitchell, S., Hayes-Guastella, L., Nathan, V., Serres, M., Shock, E., Girguis, P., German, C., Klein, F., Seewald, J., Huber, J. A.. 2026-07-01. Microbial Growth in an Enceladus Ocean Analog Medium Informed by Mineral Stability Modeling. https://doi.org/10.64898/2026.06.29.735333

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