3.5 billion years of glass bioalteration: Volcanic rocks as a basis for microbial life? |
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| Institution: | 1. Scripps Institution of Oceanography, University of California, La Jolla, CA 92093-0225, USA;2. Department of Earth Science & Centre for Geobiology, University of Bergen, Allegt. 41, 5007 Bergen, Norway;3. Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada N6A 5B7;4. School of Marine Sciences, University of Maine, Orono, ME, 04469, USA;5. Department of Geological Sciences, 2200 Colorado Ave., University of Colorado, Boulder, CO 80309-0399, USA;1. Department of Molecular Biosciences and Bioengineering, 1955 East West Rd. Ag. Science #218, University of Hawai?i at Manoa, HI 96822, USA;2. Hawai?i Natural Energy Institute, 1680 East West Rd. POST #109, University of Hawai?i at Manoa, HI 96822, USA;1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Biointerfaces, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland;2. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Protection and Physiology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland;1. Department of Arid Zone Management, Faculty of Rangeland and Watershed Management, Gorgan University of Agricultural Sciences & Natural Resources, Gorgan, Iran;2. Department of Natural Resources and Environmental Engineering, College of Agriculture, Shiraz University, Shiraz, Iran;3. Department of Geography, Texas State University, San Marcos, TX, United States;1. Centre for Planetary Science and Exploration/Department of Earth Sciences, University of Western Ontario, 1151 Richmond St, London, Ontario, N6A 5B7, Canada;2. Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond St, London, Ontario, N6A 5B7, Canada |
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| Abstract: | Alteration textures in volcanic glass from the seafloor fall into two classes, one suggestive of abiotic/diffusive hydration and chemical exchange, and another likely to be caused by microbial, cavity-forming, congruent dissolution. Glass bioalteration is common in submarine lavas throughout the world's ocean, dominant in the upper 300 m of the oceanic crust, and found in all well-preserved ophiolites and greenstone belts dating back to 3.5 Ga. It may yield a significant fraction of the global biomass and geochemical fluxes and is relevant to the development of the earliest life on Earth. We present a critical review concerning these glass bioalteration textures and present new data on their microchemical environment. We explore arguments for their biogenicity and further develop the prevalent model for their formation by relating corrosion morphology to the mechanism of microbial dissolution. Biological alteration produces conspicuous micron-scale granular and tubular textures. Granular glass alteration is well explained by colonizing microbes that selectively dissolve the glass in their contact area, forming a sponge-like interconnected network of micron-sized cavities along glass surfaces. Tubular alteration meanwhile, is more likely to be caused by filamentous cell extensions in a process similar to fungal tunneling of soil feldspars and marine carbonates. While we see clear functional similarities to fungal dissolution behavior, we do not know whether fungal or prokaryotic organisms are involved. However, this functional constraint may eventually help to identify potential microbes responsible for these features, potentially including eukaryotic or prokaryotic organisms. Yet, we caution that these organisms may be difficult to identify and to study, because they are likely to be sparsely distributed, slow growing, and difficult to cultivate. |
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