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Abstract EANA2025-24 |
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Culture of extremophilic microorganisms into Enceladus-like conditions: in search of biosignatures for future space missions
The search for extraterrestrial life emphasizes the importance of understanding how microorganisms can survive in extreme physicochemical conditions. Methanothermococcus okinawensis, a thermophilic, hydrogenotrophic methanogenic archaeon that was isolated from a deep-sea hydrothermal system (Takai et al., 2002), is a relevant model organism with which to assess the habitability of icy worlds such as Enceladus (Taubner et al., 2018; Cable at al. 2021).
In this study, M. okinawensis was cultured under 15 different laboratory conditions mimicking the oceanic environment of Enceladus which include variations in pH, salinity, and the presence of potential growth inhibitors (NH₄Cl, CH₃OH). Methane production kinetics were monitored over time for each culture, providing insight into metabolic activity and stress tolerance. Cell morphology was assessed by microscopy to evaluate physiological responses to environmental constraints.
Preliminary results show a strong modulation of both growth and methane production depending on the type and combination of inhibitors present. While M. okinawensis exhibited robust methane production under moderate stress, extreme alkaline conditions and the combined presence of ammonium chloride and methanol significantly impaired both metabolic activity and cell integrity.
In parallel, the gaseous phases were analyzed using gas chromatography coupled to a mass spectrometer with a focus on H₂S quantification as a potential indirect indicator of life-related processes. Data interpretation is ongoing, showing promising trends that correlates H₂S production with specific stress conditions.
This multidisciplinary approach, combining growth kinetics, cell morphology, and chemical analyses, strengthens our understanding of methanogen adaptation to extraterrestrial-like environments. It refines the range of biosignatures that may be accessible to future astrobiological missions exploring the subsurface ocean of Enceladus (Cable et al., 2021; MacKenzie et al., 2022).
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MacKenzie, S. M., Neveu, M., Davila, A. F., Lunine, J. I., Cable, M. L., Phillips-Lander, C. M., ... & Heldmann, J. (2022). Science objectives for flagship-class mission concepts for the search for evidence of life at Enceladus. Astrobiology, 22(6), 685-712. doi.org/10.1089/ast.2020.2425
Takai, K., Inoue, A., & Horikoshi, K. (2002). Methanothermococcus okinawensis sp. nov., a thermophilic, methane-producing archaeon isolated from a Western Pacific deep-sea hydrothermal vent system. International journal of systematic and evolutionary microbiology, 52(4), 1089-1095. DOI:10.1099/ijs.0.02106-0
Taubner, R. S., Pappenreiter, P., Zwicker, J., Smrzka, D., Pruckner, C., Kolar, P., ... & Rittmann, S. K. M. (2018). Biological methane production under putative Enceladus-like conditions. Nature communications, 9(1), 748. https://doi.org/10.1038/s41467-018-02876-y