Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells

ABSTRACT Anode-respiring bacteria (ARB) generate electric current in microbial electrochemical cells (MXCs) by channeling electrons from the oxidation of organic substrates to an electrode. Production of high current densities by monocultures in MXCs has resulted almost exclusively from the activity...

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Autores principales:	Jonathan P. Badalamenti, Rosa Krajmalnik-Brown, César I. Torres
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/5c23b1e8544246c2af67204252df141a
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spelling	oai:doaj.org-article:5c23b1e8544246c2af67204252df141a2021-11-15T15:40:05ZGeneration of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells10.1128/mBio.00144-132150-7511https://doaj.org/article/5c23b1e8544246c2af67204252df141a2013-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00144-13https://doaj.org/toc/2150-7511ABSTRACT Anode-respiring bacteria (ARB) generate electric current in microbial electrochemical cells (MXCs) by channeling electrons from the oxidation of organic substrates to an electrode. Production of high current densities by monocultures in MXCs has resulted almost exclusively from the activity of Geobacter sulfurreducens, a neutrophilic freshwater Fe(III)-reducing bacterium and the highest-current-producing member documented for the Geobacteraceae family of the Deltaproteobacteria. Here we report high current densities generated by haloalkaliphilic Geoalkalibacter spp., thus broadening the capability for high anode respiration rates by including other genera within the Geobacteraceae. In this study, acetate-fed pure cultures of two related Geoalkalibacter spp. produced current densities of 5.0 to 8.3 and 2.4 to 3.3 A m−2 under alkaline (pH 9.3) and saline (1.7% NaCl) conditions, respectively. Chronoamperometric studies of halophilic Glk. subterraneus DSM 23483 and alkaliphilic Glk. ferrihydriticus DSM 17813 suggested that cells performed long-range electron transfer through electrode-attached biofilms and not through soluble electron shuttles. Glk. ferrihydriticus also oxidized ethanol directly to produce current, with maximum current densities of 5.7 to 7.1 A m−2 and coulombic efficiencies of 84 to 95%. Cyclic voltammetry (CV) elicited a sigmoidal response with characteristic onset, midpoint, and saturation potentials, while CV performed in the absence of an electron donor suggested the involvement of redox molecules in the biofilm that were limited by diffusion. These results matched those previously reported for actively respiring Gb. sulfurreducens biofilms producing similar current densities (~5 to 9 A m−2). IMPORTANCE This study establishes the highest current densities ever achieved by pure cultures of anode-respiring bacteria (ARB) under alkaline and saline conditions in microbial electrochemical cells (MXCs) and provides the first electrochemical characterization of the genus Geoalkalibacter. Production of high current densities among the Geobacteraceae is no longer exclusive to Geobacter sulfurreducens, suggesting greater versatility for this family in fundamental and applied microbial electrochemical cell (MXC) research than previously considered. Additionally, this work raises the possibility that different members of the Geobacteraceae have conserved molecular mechanisms governing respiratory extracellular electron transfer to electrodes. Thus, the capacity for high current generation may exist in other uncultivated members of this family. Advancement of MXC technology for practical uses must rely on an expanded suite of ARB capable of using different electron donors and producing high current densities under various conditions. Geoalkalibacter spp. can potentially broaden the practical capabilities of MXCs to include energy generation and waste treatment under expanded ranges of salinity and pH.Jonathan P. BadalamentiRosa Krajmalnik-BrownCésar I. TorresAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 3 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Jonathan P. Badalamenti Rosa Krajmalnik-Brown César I. Torres Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells
description	ABSTRACT Anode-respiring bacteria (ARB) generate electric current in microbial electrochemical cells (MXCs) by channeling electrons from the oxidation of organic substrates to an electrode. Production of high current densities by monocultures in MXCs has resulted almost exclusively from the activity of Geobacter sulfurreducens, a neutrophilic freshwater Fe(III)-reducing bacterium and the highest-current-producing member documented for the Geobacteraceae family of the Deltaproteobacteria. Here we report high current densities generated by haloalkaliphilic Geoalkalibacter spp., thus broadening the capability for high anode respiration rates by including other genera within the Geobacteraceae. In this study, acetate-fed pure cultures of two related Geoalkalibacter spp. produced current densities of 5.0 to 8.3 and 2.4 to 3.3 A m−2 under alkaline (pH 9.3) and saline (1.7% NaCl) conditions, respectively. Chronoamperometric studies of halophilic Glk. subterraneus DSM 23483 and alkaliphilic Glk. ferrihydriticus DSM 17813 suggested that cells performed long-range electron transfer through electrode-attached biofilms and not through soluble electron shuttles. Glk. ferrihydriticus also oxidized ethanol directly to produce current, with maximum current densities of 5.7 to 7.1 A m−2 and coulombic efficiencies of 84 to 95%. Cyclic voltammetry (CV) elicited a sigmoidal response with characteristic onset, midpoint, and saturation potentials, while CV performed in the absence of an electron donor suggested the involvement of redox molecules in the biofilm that were limited by diffusion. These results matched those previously reported for actively respiring Gb. sulfurreducens biofilms producing similar current densities (~5 to 9 A m−2). IMPORTANCE This study establishes the highest current densities ever achieved by pure cultures of anode-respiring bacteria (ARB) under alkaline and saline conditions in microbial electrochemical cells (MXCs) and provides the first electrochemical characterization of the genus Geoalkalibacter. Production of high current densities among the Geobacteraceae is no longer exclusive to Geobacter sulfurreducens, suggesting greater versatility for this family in fundamental and applied microbial electrochemical cell (MXC) research than previously considered. Additionally, this work raises the possibility that different members of the Geobacteraceae have conserved molecular mechanisms governing respiratory extracellular electron transfer to electrodes. Thus, the capacity for high current generation may exist in other uncultivated members of this family. Advancement of MXC technology for practical uses must rely on an expanded suite of ARB capable of using different electron donors and producing high current densities under various conditions. Geoalkalibacter spp. can potentially broaden the practical capabilities of MXCs to include energy generation and waste treatment under expanded ranges of salinity and pH.
format	article
author	Jonathan P. Badalamenti Rosa Krajmalnik-Brown César I. Torres
author_facet	Jonathan P. Badalamenti Rosa Krajmalnik-Brown César I. Torres
author_sort	Jonathan P. Badalamenti
title	Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells
title_short	Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells
title_full	Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells
title_fullStr	Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells
title_full_unstemmed	Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells
title_sort	generation of high current densities by pure cultures of anode-respiring <italic toggle="yes">geoalkalibacter</italic> spp. under alkaline and saline conditions in microbial electrochemical cells
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/5c23b1e8544246c2af67204252df141a
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Generation of High Current Densities by Pure Cultures of Anode-Respiring <italic toggle="yes">Geoalkalibacter</italic> spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells

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