Enceladus-like geochemistry fuels methanogenesis under extreme CO₂ limitation.

Authors

Vanessa Helmbrecht, Frank Postberg, Nozair Khawaja, Robert Reichelt, Frieder Klein, Dina Grohmann, William D Orsi

Published in

Science advances. Volume 12. Issue 39. Pages eaei0167. Sep 25, 2026. Epub Sep 25, 2026.

Abstract

Saturn's icy moon Enceladus features chemical signatures consistent with an alkaline soda ocean with H₂ production via hydrothermal water-rock reactions. Chemolithoautotrophic methanogenesis is thermodynamically favorable under these conditions, but it is unknown whether CO₂ scarcity in the alkaline Enceladus soda ocean limits autotrophy. Here, we show that simulated Enceladus' ocean chemistry containing high concentrations of dissolved inorganic carbon and H₂ from mineral-water reactions enables growth of the chemolithoautotroph H₂-oxidizing methanogen Methanothermococcus okinawensis until pH 11, far exceeding its previously known pH limit. Transcriptomics revealed that growing cells overcome CO₂ scarcity in the simulated Enceladus soda ocean by overexpressing the reductive acetyl-CoA pathway for CO₂ fixation, which enabled efficient scavenging of CO₂ at extremely low concentrations. The carbon and energy metabolism of M. okinawensis was entirely fueled by the abiotic H₂ derived from the simulated Enceladus mineral-water reactions.

PMID:
42789704
Bibliographic data and abstract were imported from PubMed on 26 Sep 2026.

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