Biological Methane Production under putative Enceladus-like conditions

Ruth-Sophie Taubner, Patricia Pappenreiter, Jennifer Zwicker, Daniel Smrzka, Christian Pruckner, Philipp Kolar, Sebastian Bernacchi, Arne H Seifert, Alexander Krajete, Wolfgang Bach, Jörn Peckmann, Christian Paulik, Maria Gertrude Firneis, Christa Schleper, Simon Karl-Maria Rasso Rittmann

More than ten years ago, NASA’s Cassini mission put a spotlight on Saturn’s icy moon Enceladus. Several studies about putative ongoing geochemical activities inside the moon, like hydrothermal vents or serpentinization attracted the attention of the astrobiological community. Serpentinization of olivine, i.e.the oxidation of native and ferrous iron, may be the most prominent potential source of molecular hydrogen (H2) in Enceladus’ interior. In addition, many different organic and inorganic molecules like water (H2O), methane (CH4), carbon dioxide (CO2), and ammonia (NH3) were detected in the plume. Thus, Enceladus harbours the necessary basic ingredients for life. The most promising area on Enceladus where life may exist is at the seafloor of the ice-covered ocean, where pressure was estimated to be 35 to 80 bar.Possible life forms on Enceladus must be chemoautotrophic, i.e.independent of products of photosynthesis, and would need to be anaerobic, i.e.independent of oxygen. Among the organisms that meet these characteristicsare methanogenic archaea. In this study we raise the question, if some of the CH4detected in the plume might originate in methanogenic activity.To explore if methanogens can produce CH4under Enceladus-like conditions, we studied three hydrogenotrophicarchaea (Methanothermococcus okinawensis,Methanothermobacter marburgensis,and Methanococcus villosus). While mimicking potential physical conditions of Enceladus’ ocean (65/80°C, 10-90 bar) we also performed experiments aimed to elucidate the tolerance towards potential gaseous and liquid inhibitors detected in Enceladus’ plume (high NH3levels, formaldehyde, ethene, and methanol). In particular, M. okinawensis, the isolate from a deep marine trench, showed tolerance towards all of the added inhibitors and maintained methanogenesis up to 50 bar. We conclude that methanogenesis could in principle be feasible under putative Enceladus-like conditions.

Department für Ökogenomik und Systembiologie, Department für Geodynamik und Sedimentologie, Institut für Astrophysik
Externe Organisation(en)
Krajete GmbH, Austria, Universität Bremen, Jacobs Universität Bremen, Universität Hamburg, Johannes Kepler Universität Linz
ÖFOS 2012
Industrielle Biotechnologie
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