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Metalliferous Biosignatures for Deep Subsurface Microbial Activity

The interaction of microbes and metals is widely assumed to have occurred in surface or very shallow subsurface environments. However new evidence suggests that much microbial activity occurs in the deep subsurface. Fluvial, lacustrine and aeolian ‘red beds’ contain widespread centimetre-scale reduc...

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Autores principales: Parnell, John, Brolly, Connor, Spinks, Sam, Bowden, Stephen
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Netherlands 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4679111/
https://www.ncbi.nlm.nih.gov/pubmed/26376912
http://dx.doi.org/10.1007/s11084-015-9466-x
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author Parnell, John
Brolly, Connor
Spinks, Sam
Bowden, Stephen
author_facet Parnell, John
Brolly, Connor
Spinks, Sam
Bowden, Stephen
author_sort Parnell, John
collection PubMed
description The interaction of microbes and metals is widely assumed to have occurred in surface or very shallow subsurface environments. However new evidence suggests that much microbial activity occurs in the deep subsurface. Fluvial, lacustrine and aeolian ‘red beds’ contain widespread centimetre-scale reduction spheroids in which a pale reduced spheroid in otherwise red rocks contains a metalliferous core. Most of the reduction of Fe (III) in sediments is caused by Fe (III) reducing bacteria. They have the potential to reduce a range of metals and metalloids, including V, Cu, Mo, U and Se, by substituting them for Fe (III) as electron acceptors, which are all elements common in reduction spheroids. The spheroidal morphology indicates that they were formed at depth, after compaction, which is consistent with a microbial formation. Given that the consequences of Fe (III) reduction have a visual expression, they are potential biosignatures during exploration of the terrestrial and extraterrestrial geological record. There is debate about the energy available from Fe (III) reduction on Mars, but the abundance of iron in Martian soils makes it one of the most valuable prospects for life there. Entrapment of the microbes themselves as fossils is possible, but a more realistic target during the exploration of Mars would be the colour contrasts reflecting selective reduction or oxidation. This can be achieved by analysing quartz grains across a reduction spheroid using Raman spectroscopy, which demonstrates its suitability for life detection in subsurface environments. Microbial action is the most suitable explanation for the formation of reduction spheroids and may act as metalliferous biosignatures for deep subsurface microbial activity.
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spelling pubmed-46791112015-12-22 Metalliferous Biosignatures for Deep Subsurface Microbial Activity Parnell, John Brolly, Connor Spinks, Sam Bowden, Stephen Orig Life Evol Biosph Astrobiology The interaction of microbes and metals is widely assumed to have occurred in surface or very shallow subsurface environments. However new evidence suggests that much microbial activity occurs in the deep subsurface. Fluvial, lacustrine and aeolian ‘red beds’ contain widespread centimetre-scale reduction spheroids in which a pale reduced spheroid in otherwise red rocks contains a metalliferous core. Most of the reduction of Fe (III) in sediments is caused by Fe (III) reducing bacteria. They have the potential to reduce a range of metals and metalloids, including V, Cu, Mo, U and Se, by substituting them for Fe (III) as electron acceptors, which are all elements common in reduction spheroids. The spheroidal morphology indicates that they were formed at depth, after compaction, which is consistent with a microbial formation. Given that the consequences of Fe (III) reduction have a visual expression, they are potential biosignatures during exploration of the terrestrial and extraterrestrial geological record. There is debate about the energy available from Fe (III) reduction on Mars, but the abundance of iron in Martian soils makes it one of the most valuable prospects for life there. Entrapment of the microbes themselves as fossils is possible, but a more realistic target during the exploration of Mars would be the colour contrasts reflecting selective reduction or oxidation. This can be achieved by analysing quartz grains across a reduction spheroid using Raman spectroscopy, which demonstrates its suitability for life detection in subsurface environments. Microbial action is the most suitable explanation for the formation of reduction spheroids and may act as metalliferous biosignatures for deep subsurface microbial activity. Springer Netherlands 2015-09-16 2016 /pmc/articles/PMC4679111/ /pubmed/26376912 http://dx.doi.org/10.1007/s11084-015-9466-x Text en © The Author(s) 2015 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
spellingShingle Astrobiology
Parnell, John
Brolly, Connor
Spinks, Sam
Bowden, Stephen
Metalliferous Biosignatures for Deep Subsurface Microbial Activity
title Metalliferous Biosignatures for Deep Subsurface Microbial Activity
title_full Metalliferous Biosignatures for Deep Subsurface Microbial Activity
title_fullStr Metalliferous Biosignatures for Deep Subsurface Microbial Activity
title_full_unstemmed Metalliferous Biosignatures for Deep Subsurface Microbial Activity
title_short Metalliferous Biosignatures for Deep Subsurface Microbial Activity
title_sort metalliferous biosignatures for deep subsurface microbial activity
topic Astrobiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4679111/
https://www.ncbi.nlm.nih.gov/pubmed/26376912
http://dx.doi.org/10.1007/s11084-015-9466-x
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