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Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1

Extracellular electron transfer (EET) plays a fundamental role in microbial reduction/oxidation of minerals. Extracellular polymeric substances (EPS) surrounding the cells constitute a matrix that separates the cell’s outer membrane from insoluble minerals and environmental fluid. This study investi...

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Autores principales: Gao, Lei, Lu, Xiancai, Liu, Huan, Li, Juan, Li, Weijie, Song, Rongbin, Wang, Ruiyong, Zhang, Dongmei, Zhu, Junjie
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449630/
https://www.ncbi.nlm.nih.gov/pubmed/30984128
http://dx.doi.org/10.3389/fmicb.2019.00575
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author Gao, Lei
Lu, Xiancai
Liu, Huan
Li, Juan
Li, Weijie
Song, Rongbin
Wang, Ruiyong
Zhang, Dongmei
Zhu, Junjie
author_facet Gao, Lei
Lu, Xiancai
Liu, Huan
Li, Juan
Li, Weijie
Song, Rongbin
Wang, Ruiyong
Zhang, Dongmei
Zhu, Junjie
author_sort Gao, Lei
collection PubMed
description Extracellular electron transfer (EET) plays a fundamental role in microbial reduction/oxidation of minerals. Extracellular polymeric substances (EPS) surrounding the cells constitute a matrix that separates the cell’s outer membrane from insoluble minerals and environmental fluid. This study investigated the effects of EPS on EET processes during microbial reduction of hematite by the iron-reducing strain Shewanella oneidensis MR-1 (MR-1). Electrochemical characterization techniques were employed to determine the influence of EPS components on the redox ability of MR-1. Cells with removed EPS exhibited approximately 30% higher hematite reduction than regular MR-1 cells, and produced a current density of 56 μA cm(-2), corresponding to 3–4 fold that of regular MR-1. The superior EET of EPS-deprived cells could be attributed to direct contact between outer membrane proteins and hematite surface, as indicated by more redox peaks being detected by cyclic voltammetry and differential pulse voltammetry. The significantly reduced current density of MR-1 cells treated with proteinase K and deoxyribonuclease suggests that the electron transfer capacity across the EPS layer depends mainly on the spatial distribution of specific proteins and electron shuttles. Exopolysaccharides in EPS tend to inhibit electron transfer, however they also favor the attachment of cells onto hematite surfaces. Consistently, the charge transfer resistance of cells lacking EPS was only 116.3 Ω, approximately 44 times lower than that of regular cells (5,139.1 Ω). These findings point to a negative influence of EPS on EET processes for microbial reduction/oxidation of minerals.
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spelling pubmed-64496302019-04-12 Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1 Gao, Lei Lu, Xiancai Liu, Huan Li, Juan Li, Weijie Song, Rongbin Wang, Ruiyong Zhang, Dongmei Zhu, Junjie Front Microbiol Microbiology Extracellular electron transfer (EET) plays a fundamental role in microbial reduction/oxidation of minerals. Extracellular polymeric substances (EPS) surrounding the cells constitute a matrix that separates the cell’s outer membrane from insoluble minerals and environmental fluid. This study investigated the effects of EPS on EET processes during microbial reduction of hematite by the iron-reducing strain Shewanella oneidensis MR-1 (MR-1). Electrochemical characterization techniques were employed to determine the influence of EPS components on the redox ability of MR-1. Cells with removed EPS exhibited approximately 30% higher hematite reduction than regular MR-1 cells, and produced a current density of 56 μA cm(-2), corresponding to 3–4 fold that of regular MR-1. The superior EET of EPS-deprived cells could be attributed to direct contact between outer membrane proteins and hematite surface, as indicated by more redox peaks being detected by cyclic voltammetry and differential pulse voltammetry. The significantly reduced current density of MR-1 cells treated with proteinase K and deoxyribonuclease suggests that the electron transfer capacity across the EPS layer depends mainly on the spatial distribution of specific proteins and electron shuttles. Exopolysaccharides in EPS tend to inhibit electron transfer, however they also favor the attachment of cells onto hematite surfaces. Consistently, the charge transfer resistance of cells lacking EPS was only 116.3 Ω, approximately 44 times lower than that of regular cells (5,139.1 Ω). These findings point to a negative influence of EPS on EET processes for microbial reduction/oxidation of minerals. Frontiers Media S.A. 2019-03-29 /pmc/articles/PMC6449630/ /pubmed/30984128 http://dx.doi.org/10.3389/fmicb.2019.00575 Text en Copyright © 2019 Gao, Lu, Liu, Li, Li, Song, Wang, Zhang and Zhu. 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) and the copyright owner(s) 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
Gao, Lei
Lu, Xiancai
Liu, Huan
Li, Juan
Li, Weijie
Song, Rongbin
Wang, Ruiyong
Zhang, Dongmei
Zhu, Junjie
Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1
title Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1
title_full Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1
title_fullStr Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1
title_full_unstemmed Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1
title_short Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1
title_sort mediation of extracellular polymeric substances in microbial reduction of hematite by shewanella oneidensis mr-1
topic Microbiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449630/
https://www.ncbi.nlm.nih.gov/pubmed/30984128
http://dx.doi.org/10.3389/fmicb.2019.00575
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