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Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement

This contribution assesses the availability of catabolic energy for microbial life during water–rock reactions in the flanks of mid-ocean ridges, where basaltic and ultramafic rocks interact with circulating seawater. In addition to equilibrium thermodynamic computations, results for kinetic reactio...

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Autor principal: Bach, Wolfgang
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4746428/
https://www.ncbi.nlm.nih.gov/pubmed/26903986
http://dx.doi.org/10.3389/fmicb.2016.00107
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author Bach, Wolfgang
author_facet Bach, Wolfgang
author_sort Bach, Wolfgang
collection PubMed
description This contribution assesses the availability of catabolic energy for microbial life during water–rock reactions in the flanks of mid-ocean ridges, where basaltic and ultramafic rocks interact with circulating seawater. In addition to equilibrium thermodynamic computations, results for kinetic reaction paths are presented. In these calculations, it is assumed that dissolution of olivine and basalt glass control the rates of hydrogen forming reactions in ultramafic and basaltic rocks, respectively. The results suggest that all ocean crust basement rocks release enough hydrogen (H(2),aq) to support hydrogenotrophic life at low water-to-rock ratios. Olivine dissolution rate control imposes a stronger effect on hydrogen production than phase equilibrium controls, indicating that magnetite formation is not a requirement for production of large amounts of hydrogen in ultramafic rocks. The formation of non-tronite and celadonite are primarily responsible for the formation of the moderate amounts of hydrogen (H(2),aq) expected in basaltic ridge flanks. Under conditions of large seawater fluxes required to account for the great global convective heat flow in ridge flanks, however, hydrogen production in basaltic ridge flanks is insufficient for supporting hydrogenotrophic life. It is hence proposed that the role of Fe oxidation in basaltic ridge flanks is greater than previously suggested. A standing stock of 2.4(∗)10(28) cells may be supported by Fe oxidation in basaltic ridge flanks, equivalent of about 10% of the sedimentary deep biosphere. The size of a hydrogenotrophic biomass within the ocean crust is more difficult to estimate because the rates and processes of hydrogen release are insufficiently constrained. In any case, hydrogenotrophy in the ocean crust should be of key importance only in olivine-rich basement rocks and in sedimented ridge flanks with low time-integrated seawater fluxes.
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spelling pubmed-47464282016-02-22 Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement Bach, Wolfgang Front Microbiol Microbiology This contribution assesses the availability of catabolic energy for microbial life during water–rock reactions in the flanks of mid-ocean ridges, where basaltic and ultramafic rocks interact with circulating seawater. In addition to equilibrium thermodynamic computations, results for kinetic reaction paths are presented. In these calculations, it is assumed that dissolution of olivine and basalt glass control the rates of hydrogen forming reactions in ultramafic and basaltic rocks, respectively. The results suggest that all ocean crust basement rocks release enough hydrogen (H(2),aq) to support hydrogenotrophic life at low water-to-rock ratios. Olivine dissolution rate control imposes a stronger effect on hydrogen production than phase equilibrium controls, indicating that magnetite formation is not a requirement for production of large amounts of hydrogen in ultramafic rocks. The formation of non-tronite and celadonite are primarily responsible for the formation of the moderate amounts of hydrogen (H(2),aq) expected in basaltic ridge flanks. Under conditions of large seawater fluxes required to account for the great global convective heat flow in ridge flanks, however, hydrogen production in basaltic ridge flanks is insufficient for supporting hydrogenotrophic life. It is hence proposed that the role of Fe oxidation in basaltic ridge flanks is greater than previously suggested. A standing stock of 2.4(∗)10(28) cells may be supported by Fe oxidation in basaltic ridge flanks, equivalent of about 10% of the sedimentary deep biosphere. The size of a hydrogenotrophic biomass within the ocean crust is more difficult to estimate because the rates and processes of hydrogen release are insufficiently constrained. In any case, hydrogenotrophy in the ocean crust should be of key importance only in olivine-rich basement rocks and in sedimented ridge flanks with low time-integrated seawater fluxes. Frontiers Media S.A. 2016-02-09 /pmc/articles/PMC4746428/ /pubmed/26903986 http://dx.doi.org/10.3389/fmicb.2016.00107 Text en Copyright © 2016 Bach. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Microbiology
Bach, Wolfgang
Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement
title Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement
title_full Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement
title_fullStr Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement
title_full_unstemmed Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement
title_short Some Compositional and Kinetic Controls on the Bioenergetic Landscapes in Oceanic Basement
title_sort some compositional and kinetic controls on the bioenergetic landscapes in oceanic basement
topic Microbiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4746428/
https://www.ncbi.nlm.nih.gov/pubmed/26903986
http://dx.doi.org/10.3389/fmicb.2016.00107
work_keys_str_mv AT bachwolfgang somecompositionalandkineticcontrolsonthebioenergeticlandscapesinoceanicbasement