Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity

ABSTRACT The electrically conductive pili (e-pili) of Geobacter sulfurreducens serve as a model for a novel strategy for long-range extracellular electron transfer. e-pili are also a new class of bioelectronic materials. However, the only other Geobacter pili previously studied, which were from G. u...

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Autores principales:	Yang Tan, Ramesh Y. Adhikari, Nikhil S. Malvankar, Joy E. Ward, Trevor L. Woodard, Kelly P. Nevin, Derek R. Lovley
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2017
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/482ada20f89c48d68cc5802955d6a878
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spelling	oai:doaj.org-article:482ada20f89c48d68cc5802955d6a8782021-11-15T15:51:07ZExpressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity10.1128/mBio.02203-162150-7511https://doaj.org/article/482ada20f89c48d68cc5802955d6a8782017-03-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02203-16https://doaj.org/toc/2150-7511ABSTRACT The electrically conductive pili (e-pili) of Geobacter sulfurreducens serve as a model for a novel strategy for long-range extracellular electron transfer. e-pili are also a new class of bioelectronic materials. However, the only other Geobacter pili previously studied, which were from G. uraniireducens, were poorly conductive. In order to obtain more information on the range of pili conductivities in Geobacter species, the pili of G. metallireducens were investigated. Heterologously expressing the PilA gene of G. metallireducens in G. sulfurreducens yielded a G. sulfurreducens strain, designated strain MP, that produced abundant pili. Strain MP exhibited phenotypes consistent with the presence of e-pili, such as high rates of Fe(III) oxide reduction and high current densities on graphite anodes. Individual pili prepared at physiologically relevant pH 7 had conductivities of 277 ± 18.9 S/cm (mean ± standard deviation), which is 5,000-fold higher than the conductivity of G. sulfurreducens pili at pH 7 and nearly 1 million-fold higher than the conductivity of G. uraniireducens pili at the same pH. A potential explanation for the higher conductivity of the G. metallireducens pili is their greater density of aromatic amino acids, which are known to be important components in electron transport along the length of the pilus. The G. metallireducens pili represent the most highly conductive pili found to date and suggest strategies for designing synthetic pili with even higher conductivities. IMPORTANCE e-pili are a remarkable electrically conductive material that can be sustainably produced without harsh chemical processes from renewable feedstocks and that contain no toxic components in the final product. Thus, e-pili offer an unprecedented potential for developing novel materials, electronic devices, and sensors for diverse applications with a new “green” technology. Increasing e-pili conductivity will even further expand their potential applications. A proven strategy is to design synthetic e-pili that contain tryptophan, an aromatic amino acid not found in previously studied e-pili. The studies reported here demonstrate that a productive alternative approach is to search more broadly in the microbial world. Surprisingly, even though G. metallireducens and G. sulfurreducens are closely related, the conductivities of their e-pili differ by more than 3 orders of magnitude. The ability to produce e-pili with high conductivity without generating a genetically modified product enhances the attractiveness of this novel electronic material.Yang TanRamesh Y. AdhikariNikhil S. MalvankarJoy E. WardTrevor L. WoodardKelly P. NevinDerek R. LovleyAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 8, Iss 1 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Yang Tan Ramesh Y. Adhikari Nikhil S. Malvankar Joy E. Ward Trevor L. Woodard Kelly P. Nevin Derek R. Lovley Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity
description	ABSTRACT The electrically conductive pili (e-pili) of Geobacter sulfurreducens serve as a model for a novel strategy for long-range extracellular electron transfer. e-pili are also a new class of bioelectronic materials. However, the only other Geobacter pili previously studied, which were from G. uraniireducens, were poorly conductive. In order to obtain more information on the range of pili conductivities in Geobacter species, the pili of G. metallireducens were investigated. Heterologously expressing the PilA gene of G. metallireducens in G. sulfurreducens yielded a G. sulfurreducens strain, designated strain MP, that produced abundant pili. Strain MP exhibited phenotypes consistent with the presence of e-pili, such as high rates of Fe(III) oxide reduction and high current densities on graphite anodes. Individual pili prepared at physiologically relevant pH 7 had conductivities of 277 ± 18.9 S/cm (mean ± standard deviation), which is 5,000-fold higher than the conductivity of G. sulfurreducens pili at pH 7 and nearly 1 million-fold higher than the conductivity of G. uraniireducens pili at the same pH. A potential explanation for the higher conductivity of the G. metallireducens pili is their greater density of aromatic amino acids, which are known to be important components in electron transport along the length of the pilus. The G. metallireducens pili represent the most highly conductive pili found to date and suggest strategies for designing synthetic pili with even higher conductivities. IMPORTANCE e-pili are a remarkable electrically conductive material that can be sustainably produced without harsh chemical processes from renewable feedstocks and that contain no toxic components in the final product. Thus, e-pili offer an unprecedented potential for developing novel materials, electronic devices, and sensors for diverse applications with a new “green” technology. Increasing e-pili conductivity will even further expand their potential applications. A proven strategy is to design synthetic e-pili that contain tryptophan, an aromatic amino acid not found in previously studied e-pili. The studies reported here demonstrate that a productive alternative approach is to search more broadly in the microbial world. Surprisingly, even though G. metallireducens and G. sulfurreducens are closely related, the conductivities of their e-pili differ by more than 3 orders of magnitude. The ability to produce e-pili with high conductivity without generating a genetically modified product enhances the attractiveness of this novel electronic material.
format	article
author	Yang Tan Ramesh Y. Adhikari Nikhil S. Malvankar Joy E. Ward Trevor L. Woodard Kelly P. Nevin Derek R. Lovley
author_facet	Yang Tan Ramesh Y. Adhikari Nikhil S. Malvankar Joy E. Ward Trevor L. Woodard Kelly P. Nevin Derek R. Lovley
author_sort	Yang Tan
title	Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity
title_short	Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity
title_full	Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity
title_fullStr	Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity
title_full_unstemmed	Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity
title_sort	expressing the <italic toggle="yes">geobacter metallireducens</italic> pila in <italic toggle="yes">geobacter sulfurreducens</italic> yields pili with exceptional conductivity
publisher	American Society for Microbiology
publishDate	2017
url	https://doaj.org/article/482ada20f89c48d68cc5802955d6a878
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Expressing the <italic toggle="yes">Geobacter metallireducens</italic> PilA in <italic toggle="yes">Geobacter sulfurreducens</italic> Yields Pili with Exceptional Conductivity

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