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Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens
Geobacter sulfurreducens uses at least two different pathways to transport electrons out of the inner membrane quinone pool before reducing acceptors beyond the outer membrane. When growing on electrodes poised at oxidizing potentials, the CbcL-dependent pathway operates at or below redox potentials...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Nature Publishing Group
2017
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322298/ https://www.ncbi.nlm.nih.gov/pubmed/28045456 http://dx.doi.org/10.1038/ismej.2016.146 |
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author | Levar, Caleb E Hoffman, Colleen L Dunshee, Aubrey J Toner, Brandy M Bond, Daniel R |
author_facet | Levar, Caleb E Hoffman, Colleen L Dunshee, Aubrey J Toner, Brandy M Bond, Daniel R |
author_sort | Levar, Caleb E |
collection | PubMed |
description | Geobacter sulfurreducens uses at least two different pathways to transport electrons out of the inner membrane quinone pool before reducing acceptors beyond the outer membrane. When growing on electrodes poised at oxidizing potentials, the CbcL-dependent pathway operates at or below redox potentials of –0.10 V vs the standard hydrogen electrode, whereas the ImcH-dependent pathway operates only above this value. Here, we provide evidence that G. sulfurreducens also requires different electron transfer proteins for reduction of a wide range of Fe(III)- and Mn(IV)-(oxyhydr)oxides, and must transition from a high- to low-potential pathway during reduction of commonly studied soluble and insoluble metal electron acceptors. Freshly precipitated Fe(III)-(oxyhydr)oxides could not be reduced by mutants lacking the high-potential pathway. Aging these minerals by autoclaving did not change their powder X-ray diffraction pattern, but restored reduction by mutants lacking the high-potential pathway. Mutants lacking the low-potential, CbcL-dependent pathway had higher growth yields with both soluble and insoluble Fe(III). Together, these data suggest that the ImcH-dependent pathway exists to harvest additional energy when conditions permit, and CbcL switches on to allow respiration closer to thermodynamic equilibrium conditions. With evidence of multiple pathways within a single organism, the study of extracellular respiration should consider not only the crystal structure or solubility of a mineral electron acceptor, but rather the redox potential, as this variable determines the energetic reward affecting reduction rates, extents, and final microbial growth yields in the environment. |
format | Online Article Text |
id | pubmed-5322298 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2017 |
publisher | Nature Publishing Group |
record_format | MEDLINE/PubMed |
spelling | pubmed-53222982017-03-01 Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens Levar, Caleb E Hoffman, Colleen L Dunshee, Aubrey J Toner, Brandy M Bond, Daniel R ISME J Original Article Geobacter sulfurreducens uses at least two different pathways to transport electrons out of the inner membrane quinone pool before reducing acceptors beyond the outer membrane. When growing on electrodes poised at oxidizing potentials, the CbcL-dependent pathway operates at or below redox potentials of –0.10 V vs the standard hydrogen electrode, whereas the ImcH-dependent pathway operates only above this value. Here, we provide evidence that G. sulfurreducens also requires different electron transfer proteins for reduction of a wide range of Fe(III)- and Mn(IV)-(oxyhydr)oxides, and must transition from a high- to low-potential pathway during reduction of commonly studied soluble and insoluble metal electron acceptors. Freshly precipitated Fe(III)-(oxyhydr)oxides could not be reduced by mutants lacking the high-potential pathway. Aging these minerals by autoclaving did not change their powder X-ray diffraction pattern, but restored reduction by mutants lacking the high-potential pathway. Mutants lacking the low-potential, CbcL-dependent pathway had higher growth yields with both soluble and insoluble Fe(III). Together, these data suggest that the ImcH-dependent pathway exists to harvest additional energy when conditions permit, and CbcL switches on to allow respiration closer to thermodynamic equilibrium conditions. With evidence of multiple pathways within a single organism, the study of extracellular respiration should consider not only the crystal structure or solubility of a mineral electron acceptor, but rather the redox potential, as this variable determines the energetic reward affecting reduction rates, extents, and final microbial growth yields in the environment. Nature Publishing Group 2017-03 2017-01-03 /pmc/articles/PMC5322298/ /pubmed/28045456 http://dx.doi.org/10.1038/ismej.2016.146 Text en Copyright © 2017 International Society for Microbial Ecology http://creativecommons.org/licenses/by-nc-sa/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/ |
spellingShingle | Original Article Levar, Caleb E Hoffman, Colleen L Dunshee, Aubrey J Toner, Brandy M Bond, Daniel R Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens |
title | Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens |
title_full | Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens |
title_fullStr | Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens |
title_full_unstemmed | Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens |
title_short | Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens |
title_sort | redox potential as a master variable controlling pathways of metal reduction by geobacter sulfurreducens |
topic | Original Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322298/ https://www.ncbi.nlm.nih.gov/pubmed/28045456 http://dx.doi.org/10.1038/ismej.2016.146 |
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