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Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors

Exoelectrogenic bacteria are defined by their ability to respire on extracellular and insoluble electron acceptors and have applications in bioremediation and microbial electrochemical systems (MESs), while playing important roles in biogeochemical cycling. Shewanella oneidensis MR-1, which has beco...

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Autores principales: Oram, Joseph, Jeuken, Lars J. C.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Society for Microbiology 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6336422/
https://www.ncbi.nlm.nih.gov/pubmed/30647155
http://dx.doi.org/10.1128/mBio.02490-18
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author Oram, Joseph
Jeuken, Lars J. C.
author_facet Oram, Joseph
Jeuken, Lars J. C.
author_sort Oram, Joseph
collection PubMed
description Exoelectrogenic bacteria are defined by their ability to respire on extracellular and insoluble electron acceptors and have applications in bioremediation and microbial electrochemical systems (MESs), while playing important roles in biogeochemical cycling. Shewanella oneidensis MR-1, which has become a model organism for the study of extracellular respiration, is known to display taxis toward insoluble electron acceptors, including electrodes. Multiple mechanisms have been proposed for MR-1’s tactic behavior, and, here, we report on the role of electrochemical potential by video microscopy cell tracking experiments in three-electrode electrochemical cells. MR-1 trajectories were determined using a particle tracking algorithm and validated with Shannon’s entropy method. Tactic response by MR-1 in the electrochemical cell was observed to depend on the applied potential, as indicated by the average velocity and density of motile (>4 µm/s) MR-1 close to the electrode (<50 µm). Tactic behavior was observed at oxidative potentials, with a strong switch between the potentials −0.15 to −0.25 V versus the standard hydrogen electrode (SHE), which coincides with the reduction potential of flavins. The average velocity and density of motile MR-1 close to the electrode increased when riboflavin was added (2 µM), but were completely absent in a ΔmtrC/ΔomcA mutant of MR-1. Besides flavin’s function as an electron mediator to support anaerobic respiration on insoluble electron acceptors, we propose that riboflavin is excreted by MR-1 to sense redox gradients in its environment, aiding taxis toward insoluble electron acceptors, including electrodes in MESs.
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spelling pubmed-63364222019-01-25 Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors Oram, Joseph Jeuken, Lars J. C. mBio Observation Exoelectrogenic bacteria are defined by their ability to respire on extracellular and insoluble electron acceptors and have applications in bioremediation and microbial electrochemical systems (MESs), while playing important roles in biogeochemical cycling. Shewanella oneidensis MR-1, which has become a model organism for the study of extracellular respiration, is known to display taxis toward insoluble electron acceptors, including electrodes. Multiple mechanisms have been proposed for MR-1’s tactic behavior, and, here, we report on the role of electrochemical potential by video microscopy cell tracking experiments in three-electrode electrochemical cells. MR-1 trajectories were determined using a particle tracking algorithm and validated with Shannon’s entropy method. Tactic response by MR-1 in the electrochemical cell was observed to depend on the applied potential, as indicated by the average velocity and density of motile (>4 µm/s) MR-1 close to the electrode (<50 µm). Tactic behavior was observed at oxidative potentials, with a strong switch between the potentials −0.15 to −0.25 V versus the standard hydrogen electrode (SHE), which coincides with the reduction potential of flavins. The average velocity and density of motile MR-1 close to the electrode increased when riboflavin was added (2 µM), but were completely absent in a ΔmtrC/ΔomcA mutant of MR-1. Besides flavin’s function as an electron mediator to support anaerobic respiration on insoluble electron acceptors, we propose that riboflavin is excreted by MR-1 to sense redox gradients in its environment, aiding taxis toward insoluble electron acceptors, including electrodes in MESs. American Society for Microbiology 2019-01-15 /pmc/articles/PMC6336422/ /pubmed/30647155 http://dx.doi.org/10.1128/mBio.02490-18 Text en Copyright © 2019 Oram and Jeuken. https://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Observation
Oram, Joseph
Jeuken, Lars J. C.
Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
title Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
title_full Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
title_fullStr Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
title_full_unstemmed Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
title_short Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
title_sort tactic response of shewanella oneidensis mr-1 toward insoluble electron acceptors
topic Observation
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6336422/
https://www.ncbi.nlm.nih.gov/pubmed/30647155
http://dx.doi.org/10.1128/mBio.02490-18
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