Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>

ABSTRACT It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro...

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Autores principales:	Madeline Vargas, Nikhil S. Malvankar, Pier-Luc Tremblay, Ching Leang, Jessica A. Smith, Pranav Patel, Oona Synoeyenbos-West, Kelly P. Nevin, Derek R. Lovley
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/48c772ce248f41fbaa9c5cbade610202
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spelling	oai:doaj.org-article:48c772ce248f41fbaa9c5cbade6102022021-11-15T15:40:27ZAromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>10.1128/mBio.00105-132150-7511https://doaj.org/article/48c772ce248f41fbaa9c5cbade6102022013-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00105-13https://doaj.org/toc/2150-7511ABSTRACT It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro-5, which produced pili with diminished conductivity. This was accomplished by modifying the amino acid sequence of PilA, the structural pilin protein. An alanine was substituted for each of the five aromatic amino acids in the carboxyl terminus of PilA, the region in which G. sulfurreducens PilA differs most significantly from the PilAs of microorganisms incapable of long-range extracellular electron transport. Strain Aro-5 produced pili that were properly decorated with the multiheme c-type cytochrome OmcS, which is essential for Fe(III) oxide reduction. However, pili preparations of the Aro-5 strain had greatly diminished conductivity and Aro-5 cultures were severely limited in their capacity to reduce Fe(III) compared to the control strain. Current production of the Aro-5 strain, with a graphite anode serving as the electron acceptor, was less than 10% of that of the control strain. The conductivity of the Aro-5 biofilms was 10-fold lower than the control strain’s. These results demonstrate that the pili of G. sulfurreducens must be conductive in order for the cells to be effective in extracellular long-range electron transport. IMPORTANCE Extracellular electron transfer by Geobacter species plays an important role in the biogeochemistry of soils and sediments and has a number of bioenergy applications. For example, microbial reduction of Fe(III) oxide is one of the most geochemically significant processes in anaerobic soils, aquatic sediments, and aquifers, and Geobacter organisms are often abundant in such environments. Geobacter sulfurreducens produces the highest current densities of any known pure culture, and close relatives are often the most abundant organisms colonizing anodes in microbial fuel cells that harvest electricity from wastewater or aquatic sediments. The finding that a strain of G. sulfurreducens that produces pili with low conductivity is limited in these extracellular electron transport functions provides further insight into these environmentally significant processes.Madeline VargasNikhil S. MalvankarPier-Luc TremblayChing LeangJessica A. SmithPranav PatelOona Synoeyenbos-WestKelly P. NevinDerek R. LovleyAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 2 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Madeline Vargas Nikhil S. Malvankar Pier-Luc Tremblay Ching Leang Jessica A. Smith Pranav Patel Oona Synoeyenbos-West Kelly P. Nevin Derek R. Lovley Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>
description	ABSTRACT It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro-5, which produced pili with diminished conductivity. This was accomplished by modifying the amino acid sequence of PilA, the structural pilin protein. An alanine was substituted for each of the five aromatic amino acids in the carboxyl terminus of PilA, the region in which G. sulfurreducens PilA differs most significantly from the PilAs of microorganisms incapable of long-range extracellular electron transport. Strain Aro-5 produced pili that were properly decorated with the multiheme c-type cytochrome OmcS, which is essential for Fe(III) oxide reduction. However, pili preparations of the Aro-5 strain had greatly diminished conductivity and Aro-5 cultures were severely limited in their capacity to reduce Fe(III) compared to the control strain. Current production of the Aro-5 strain, with a graphite anode serving as the electron acceptor, was less than 10% of that of the control strain. The conductivity of the Aro-5 biofilms was 10-fold lower than the control strain’s. These results demonstrate that the pili of G. sulfurreducens must be conductive in order for the cells to be effective in extracellular long-range electron transport. IMPORTANCE Extracellular electron transfer by Geobacter species plays an important role in the biogeochemistry of soils and sediments and has a number of bioenergy applications. For example, microbial reduction of Fe(III) oxide is one of the most geochemically significant processes in anaerobic soils, aquatic sediments, and aquifers, and Geobacter organisms are often abundant in such environments. Geobacter sulfurreducens produces the highest current densities of any known pure culture, and close relatives are often the most abundant organisms colonizing anodes in microbial fuel cells that harvest electricity from wastewater or aquatic sediments. The finding that a strain of G. sulfurreducens that produces pili with low conductivity is limited in these extracellular electron transport functions provides further insight into these environmentally significant processes.
format	article
author	Madeline Vargas Nikhil S. Malvankar Pier-Luc Tremblay Ching Leang Jessica A. Smith Pranav Patel Oona Synoeyenbos-West Kelly P. Nevin Derek R. Lovley
author_facet	Madeline Vargas Nikhil S. Malvankar Pier-Luc Tremblay Ching Leang Jessica A. Smith Pranav Patel Oona Synoeyenbos-West Kelly P. Nevin Derek R. Lovley
author_sort	Madeline Vargas
title	Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>
title_short	Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>
title_full	Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>
title_fullStr	Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>
title_full_unstemmed	Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>
title_sort	aromatic amino acids required for pili conductivity and long-range extracellular electron transport in <named-content content-type="genus-species">geobacter sulfurreducens</named-content>
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/48c772ce248f41fbaa9c5cbade610202
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Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in <named-content content-type="genus-species">Geobacter sulfurreducens</named-content>

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