Microbial diversity and activity in Southern California salterns and bitterns: analogues for remnant ocean worlds |
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| Authors: | Benjamin Klempay Nestor Arandia-Gorostidi Anne E Dekas Douglas H Bartlett Christopher E Carr Peter T Doran Avishek Dutta Natalia Erazo Luke A Fisher Jennifer B Glass Alexandra Pontefract Sanjoy M Som Jesse M Wilson Britney E Schmidt Jeff S Bowman |
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| Institution: | 1. Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037 USA;2. Department of Earth System Science, Stanford University, Stanford, CA, 94305 USA;3. Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, 30332 USA;4. Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, 70803 USA;5. School of Earth and Atmospheric Studies, Georgia Institute of Technology, Atlanta, GA, 30332 USA;6. Department of Biology, Georgetown University, Washington, DC, 20057 USA;7. Blue Marble Space Institute of Science, Seattle, WA, 98154 USA |
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| Abstract: | Concurrent osmotic and chaotropic stress make MgCl2-rich brines extremely inhospitable environments. Understanding the limits of life in these brines is essential to the search for extraterrestrial life on contemporary and relict ocean worlds, like Mars, which could host similar environments. We sequenced environmental 16S rRNA genes and quantified microbial activity across a broad range of salinity and chaotropicity at a Mars-analogue salt harvesting facility in Southern California, where seawater is evaporated in a series of ponds ranging from kosmotropic NaCl brines to highly chaotropic MgCl2 brines. Within NaCl brines, we observed a proliferation of specialized halophilic Euryarchaeota, which corresponded closely with the dominant taxa found in salterns around the world. These communities were characterized by very slow growth rates and high biomass accumulation. As salinity and chaotropicity increased, we found that the MgCl2-rich brines eventually exceeded the limits of microbial activity. We found evidence that exogenous genetic material is preserved in these chaotropic brines, producing an unexpected increase in diversity in the presumably sterile MgCl2-saturated brines. Because of their high potential for biomarker preservation, chaotropic brines could therefore serve as repositories of genetic biomarkers from nearby environments (both on Earth and beyond) making them prime targets for future life-detection missions. |
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