Cryogenic silicification of microorganisms in hydrothermal fluids
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Silica-rich hydrothermal fluids that experience freezing temperatures precipitate cryogenic opal-A (COA) within ice-bound brine channels. We investigated cryogenic silicification as a novel preservation pathway for chemo- and photo-lithotrophic Bacteria and Archaea. We find that the co-partitioning of microbial cells and silica into brine channels causes microorganisms to become fossilised in COA. Rod- and coccoidal-form Bacteria and Archaea produce numerous cell casts on COA particle surfaces, while Chloroflexus filaments are preserved inside particle interiors. COA particles precipitated from natural Icelandic hot spring fluids possess similar biomorphic casts, including those containing intact microbial cells. Biomolecules and inorganic metabolic products are also captured by COA precipitation, and are detectable with a combination of visible – shortwave infrared reflectance, FTIR, and Raman spectroscopy. We identify cryogenic silicification as a newly described mechanism by which microbial biosignatures can be preserved within silica-rich hydrothermal environments. This work has implications for the interpretation of biosignatures in relic hydrothermal settings, and for life-detection on Mars and Enceladus, where opaline silica indicative of hydrothermal activity has been detected, and freezing surface conditions predominate.
Fox-Powell , M G , Channing , A , Applin , D , Cloutis , E , Preston , L J & Cousins , C R 2018 , ' Cryogenic silicification of microorganisms in hydrothermal fluids ' Earth and Planetary Science Letters , vol. 498 , pp. 1-8 . https://doi.org/10.1016/j.epsl.2018.06.026
Earth and Planetary Science Letters
Crown Copyright ©2018 Published by Elsevier B.V. All rights reserved. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at: https://doi.org/10.1016/j.epsl.2018.06.026
Descriptionhis work was supported by The Carnegie Trust (REF: 70335), The Leverhulme Trust (REF: RPG-2016-153), and a Royal Society of Edinburgh research fellowship to CRC. EAC thanks the Canadian Space Agency, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the University of Winnipeg, and the Manitoba Research Innovations Fund for supporting the University of Winnipeg's Planetary Spectrophotometer Facility.
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