scholarly journals The Archaellum ofMethanospirillum hungateiIs Electrically Conductive

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
David J. F. Walker ◽  
Eric Martz ◽  
Dawn E. Holmes ◽  
Zimu Zhou ◽  
Stephen S. Nonnenmann ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Long Range ◽  
Electronic Materials ◽  
Protein Structures ◽  
Surface Protein ◽  
Major Advance ◽  
Electrically Conductive ◽  
Anaerobic Digesters ◽  
Content Type ◽  
Potential Applications

ABSTRACTMicrobially produced electrically conductive protein filaments are of interest because they can function as conduits for long-range biological electron transfer. They also show promise as sustainably produced electronic materials. Until now, microbially produced conductive protein filaments have been reported only for bacteria. We report here that the archaellum ofMethanospirillum hungateiis electrically conductive. This is the first demonstration that electrically conductive protein filaments have evolved inArchaea. Furthermore, the structure of theM. hungateiarchaellum was previously determined (N. Poweleit, P. Ge, H. N. Nguyen, R. R. O. Loo, et al., Nat Microbiol 2:16222, 2016,https://doi.org/10.1038/nmicrobiol.2016.222). Thus, the archaellum ofM. hungateiis the first microbially produced electrically conductive protein filament for which a structure is known. We analyzed the previously published structure and identified a core of tightly packed phenylalanines that is one likely route for electron conductance. The availability of theM. hungateiarchaellum structure is expected to substantially advance mechanistic evaluation of long-range electron transport in microbially produced electrically conductive filaments and to aid in the design of “green” electronic materials that can be microbially produced with renewable feedstocks.IMPORTANCEMicrobially produced electrically conductive protein filaments are a revolutionary, sustainably produced, electronic material with broad potential applications. The design of new protein nanowires based on the knownM. hungateiarchaellum structure could be a major advance over the current empirical design of synthetic protein nanowires from electrically conductive bacterial pili. An understanding of the diversity of outer-surface protein structures capable of electron transfer is important for developing models for microbial electrical communication with other cells and minerals in natural anaerobic environments. Extracellular electron exchange is also essential in engineered environments such as bioelectrochemical devices and anaerobic digesters converting wastes to methane. The finding that the archaellum ofM. hungateiis electrically conductive suggests that some archaea might be able to make long-range electrical connections with their external environment.

scholarly journals Protein Nanowires: the Electrification of the Microbial World and Maybe Our Own

2020 ◽  
Vol 202 (20) ◽  
Author(s):  
Derek R. Lovley ◽  
Dawn E. Holmes
Keyword(s):  
Electron Transport ◽  
Long Range ◽  
Electronic Devices ◽  
Electricity Production ◽  
Microbial World ◽  
Electrically Conductive ◽  
Anaerobic Digesters ◽  
Content Type ◽  
Type Iv ◽  
Type Iv Pilin

ABSTRACT Electrically conductive protein nanowires appear to be widespread in the microbial world and are a revolutionary “green” material for the fabrication of electronic devices. Electrically conductive pili (e-pili) assembled from type IV pilin monomers have independently evolved multiple times in microbial history as have electrically conductive archaella (e-archaella) assembled from homologous archaellin monomers. A role for e-pili in long-range (micrometer) extracellular electron transport has been demonstrated in some microbes. The surprising finding of e-pili in syntrophic bacteria and the role of e-pili as conduits for direct interspecies electron transfer have necessitated a reassessment of routes for electron flux in important methanogenic environments, such as anaerobic digesters and terrestrial wetlands. Pilin monomers similar to those found in e-pili may also be a major building block of the conductive “cables” that transport electrons over centimeter distances through continuous filaments of cable bacteria consisting of a thousand cells or more. Protein nanowires harvested from microbes have many functional and sustainability advantages over traditional nanowire materials and have already yielded novel electronic devices for sustainable electricity production, neuromorphic memory, and sensing. e-pili can be mass produced with an Escherichia coli chassis, providing a ready source of material for electronics as well as for studies on the basic mechanisms for long-range electron transport along protein nanowires. Continued exploration is required to better understand the electrification of microbial communities with microbial nanowires and to expand the “green toolbox” of sustainable materials for wiring and powering the emerging “Internet of things.”

scholarly journals The electrically conductive pili of Geobacter soli

2020 ◽  
Author(s):  
Shiyan Zhuo ◽  
Guiqin Yang ◽  
Li Zhuang
Keyword(s):  
Electron Transfer ◽  
Outer Surface ◽  
Electronic Materials ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Oxide Reduction ◽  
Electrically Conductive ◽  
Current Production ◽  
Current Densities ◽  
Pilin Gene

AbstractElectrically conductive pili (e-pili) enable electron transport over multiple cell lengths to extracellular environments and play an important role in extracellular electron transfer (EET) of Geobacter species. To date, the studies of e-pili have mainly focused on Geobacter sulfurreducens and the closely related Geobacter metallireducens because of their developed genetic manipulation systems. We investigated the role of G. soli pili in EET by directly deleting the pilin gene, pilA, which is predicted to encode e-pili. Deletion of pilA, prevented the production of pili, resulting in poor Fe(III) oxide reduction and low current production, implying that G. soli pili is required for EET. To further evaluate the conductivity of G. soli pili compared with G. sulfurreducens pili, the pilA of G. soli was heterologously expressed in G. sulfurreducens, yielding the G. sulfurreducens strain GSP. This strain produced abundant pili with similar conductivity to the control strain that expressed native G. sulfurreducens pili, consistent with G. soli as determined by direct measurement, which suggested that G. soli pili is electrically conductive. Surprisingly, strain GSP was deficient in Fe(III) oxide reduction and current production due to the impaired content of outer-surface c-type cytochromes. These results demonstrated that heterologous pili of G. sulfurreducens severely reduces the content of outer-surface c-type cytochromes and consequently eliminates the capacity for EET, which strongly suggests an attention should be paid to the content of c-type cytochromes when employing G. sulfurreducens to heterologously express pili from other microorganisms.IMPORTANCEThe studies of electrically conductive pili (e-pili) of Geobacter species are of interest because of its application prospects in electronic materials. e-Pili are considered a substitution for electronic materials due to its renewability, biodegradability and robustness. Continued exploration of additional e-pili of Geobacter soli will improve the understanding of their biological role in extracellular electron transfer and expand the range of available electronic materials. Heterologously expressing the pilin genes from phylogenetically diverse microorganisms has been proposed as an emerging approach to screen potential e-pili according to high current densities. However, our results indicated that a Geobacter sulfurreducens strain heterologously expressing a pilin gene produced low current densities that resulted from a lack of content of c-type cytochromes, which were likely to possess e-pili. These results provide referential significance to yield e-pili from diverse microorganisms.

scholarly journals Direct Observation of Electrically Conductive Pili Emanating from Geobacter sulfurreducens

2021 ◽  
Author(s):  
Xinying Liu ◽  
David Jeffrey Fraser Walker ◽  
Stephen Nonnenmann ◽  
Dezhi Sun ◽  
Derek R. Lovley
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Long Range ◽  
Geobacter Sulfurreducens ◽  
Metal Corrosion ◽  
Extracellular Electron Transfer ◽  
Wild Type ◽  
Electrically Conductive ◽  
In The Wild ◽  
Pilin Gene

Geobacter sulfurreducens is a model microbe for elucidating the mechanisms for extracellular electron transfer in several biogeochemical cycles, bioelectrochemical applications, and microbial metal corrosion. Multiple lines of evidence previously suggested that electrically conductive pili (e-pili) are an essential conduit for long-range extracellular electron transport in G. sulfurreducens. However, it has recently been reported that G. sulfurreducens does not express e-pili and that filaments comprised of multi-heme c-type cytochromes are responsible for long-range electron transport. This possibility was directly investigated by examining cells, rather than filament preparations, with atomic force microscopy. Approximately 90 % of the filaments emanating from wild-type cells had a diameter (3 nm) and conductance consistent with previous reports of e-pili harvested from G. sulfurreducens or heterologously expressed in E. coli from the G. sulfurreducens pilin gene. The remaining 10% of filaments had a morphology consistent with filaments comprised of the c-type cytochrome OmcS. A strain expressing a modified pilin gene designed to yield poorly conductive pili expressed 90 % filaments with a 3 nm diameter, but greatly reduced conductance, further indicating that the 3 nm diameter conductive filaments in the wild-type strain were e-pili. A strain in which genes for five of the most abundant outer-surface c-type cytochromes, including OmcS, was deleted yielded only 3 nm diameter filaments with the same conductance as in the wild-type. These results demonstrate that e-pili are the most abundant conductive filaments expressed by G. sulfurreducens, consistent with previous functional studies demonstrating the need for e-pili for long-range extracellular electron transfer.

scholarly journals Potential for Direct Interspecies Electron Transfer in Methanogenic Wastewater Digester Aggregates

mBio ◽  
2011 ◽  
Vol 2 (4) ◽  
Author(s):  
Masahiko Morita ◽  
Nikhil S. Malvankar ◽  
Ashley E. Franks ◽  
Zarath M. Summers ◽  
Ludovic Giloteaux ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Organic Matter ◽  
Geobacter Sulfurreducens ◽  
Anaerobic Sludge ◽  
Rrna Gene ◽  
Electrically Conductive ◽  
Content Type ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer ◽  
Anaerobic Soils

ABSTRACTMechanisms for electron transfer within microbial aggregates derived from an upflow anaerobic sludge blanket reactor converting brewery waste to methane were investigated in order to better understand the function of methanogenic consortia. The aggregates were electrically conductive, with conductivities 3-fold higher than the conductivities previously reported for dual-species aggregates ofGeobacterspecies in which the two species appeared to exchange electrons via interspecies electron transfer. The temperature dependence response of the aggregate conductance was characteristic of the organic metallic-like conductance previously described for the conductive pili ofGeobacter sulfurreducensand was inconsistent with electron conduction through minerals. Studies in which aggregates were incubated with high concentrations of potential electron donors demonstrated that the aggregates had no significant capacity for conversion of hydrogen to methane. The aggregates converted formate to methane but at rates too low to account for the rates at which that the aggregates syntrophically metabolized ethanol, an important component of the reactor influent.Geobacterspecies comprised 25% of 16S rRNA gene sequences recovered from the aggregates, suggesting thatGeobacterspecies may have contributed to some but probably not all of the aggregate conductivity. Microorganisms most closely related to the acetate-utilizingMethanosaeta conciliiaccounted for more than 90% of the sequences that could be assigned to methane producers, consistent with the poor capacity for hydrogen and formate utilization. These results demonstrate for the first time that methanogenic wastewater aggregates can be electrically conductive and suggest that direct interspecies electron transfer could be an important mechanism for electron exchange in some methanogenic systems.IMPORTANCEThe conversion of waste organic matter to methane is an important bioenergy strategy, and a similar microbial metabolism of complex organic matter in anaerobic soils and sediments plays an important role in the global carbon cycle. Studies with laboratory cultures have demonstrated that hydrogen or formate can serve as an electron shuttle between the microorganisms degrading organic compounds and methanogens. However, the importance of hydrogen and formate as intermediates in the conversion of organic matter to methane in natural communities is less clear. The possibility that microorganisms within some natural methanogenic aggregates may directly exchange electrons, rather than producing hydrogen or formate as an intermediary electron carrier, is a significant paradigm shift with implications for the modeling and design of anaerobic wastewater reactors and for understanding how methanogenic communities will respond to environmental perturbations.

scholarly journals GeobacterStrains Expressing Poorly Conductive Pili Reveal Constraints on Direct Interspecies Electron Transfer Mechanisms

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Toshiyuki Ueki ◽  
Kelly P. Nevin ◽  
Amelia-Elena Rotaru ◽  
Li-Ying Wang ◽  
Joy E. Ward ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Flow ◽  
Geobacter Sulfurreducens ◽  
Wild Type ◽  
Anaerobic Digesters ◽  
Content Type ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer ◽  
Anaerobic Soils ◽  
Pilin Gene

ABSTRACTCytochrome-to-cytochrome electron transfer and electron transfer along conduits of multiple extracellular magnetite grains are often proposed as strategies for direct interspecies electron transfer (DIET) that do not require electrically conductive pili (e-pili). However, physical evidence for these proposed DIET mechanisms has been lacking. To investigate these possibilities further, we constructedGeobacter metallireducensstrain Aro-5, in which the wild-type pilin gene was replaced with thearo-5pilin gene that was previously shown to yield poorly conductive pili inGeobacter sulfurreducensstrain Aro-5.G. metallireducensstrain Aro-5 did not reduce Fe(III) oxide and produced only low current densities, phenotypes consistent with expression of poorly conductive pili. LikeG. sulfurreducensstrain Aro-5,G. metallireducensstrain Aro-5 displayed abundant outer surface cytochromes. Cocultures initiated with wild-typeG. metallireducensas the electron-donating strain andG. sulfurreducensstrain Aro-5 as the electron-accepting strain grew via DIET. However,G. metallireducensAro-5/G. sulfurreducenswild-type cocultures did not. Cocultures initiated with the Aro-5 strains of both species grew only when amended with granular activated carbon (GAC), a conductive material known to be a conduit for DIET. Magnetite could not substitute for GAC. The inability of the two Aro-5 strains to adapt for DIET in the absence of GAC suggests that there are physical constraints on establishing DIET solely through cytochrome-to-cytochrome electron transfer or along chains of magnetite. The finding that DIET is possible with electron-accepting partners that lack highly conductive pili greatly expands the range of potential electron-accepting partners that might participate in DIET.IMPORTANCEDIET is thought to be an important mechanism for interspecies electron exchange in natural anaerobic soils and sediments in which methane is either produced or consumed, as well as in some photosynthetic mats and anaerobic digesters converting organic wastes to methane. Understanding the potential mechanisms for DIET will not only aid in modeling carbon and electron flow in these geochemically significant environments but will also be helpful for interpreting meta-omic data from as-yet-uncultured microbes in DIET-based communities and for designing strategies to promote DIET in anaerobic digesters. The results demonstrate the need to develop a better understanding of the diversity of types of e-pili in the microbial world to identify potential electron-donating partners for DIET. Novel methods for recovering as-yet-uncultivated microorganisms capable of DIET in culture will be needed to further evaluate whether DIET is possible without e-pili in the absence of conductive materials such as GAC.

scholarly journals Cytochrome OmcS is not essential for long-range electron transport in Geobacter sulfurreducens strain KN400

2020 ◽  
Author(s):  
David J. F. Walker ◽  
Yang Li ◽  
David Meier ◽  
Samantha Pinches ◽  
Dawn E. Holmes ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Long Range ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Electrically Conductive ◽  
Closely Related Species ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer ◽  
Extracellular Electron Transport

AbstractThe multi-heme c-type cytochrome OmcS, is one of the central components for extracellular electron transport in Geobacter sulfurreducens strain DL-1, but its role in other microbes, including other strains of G. sulfurreducens is currently a matter of debate. Therefore, we investigated the function of OmcS in G. sulfurreducens strain KN400, which is even more effective in extracellular electron transfer than strain DL-1. We found that deleting omcS from strain KN400 did not negatively impact the rate of Fe(III) oxide reduction and did not affect the strain’s ability to accept electrons via direct interspecies electron transfer. The OmcS-deficient strain also continued to produce conductive filaments, consistent with the concept that electrically conductive pili are the primary conduit for long-range electron transfer in G. sulfurreducens and closely related species. These findings, coupled with the lack of OmcS homologs in most other microbes capable of extracellular electron transfer, suggest that OmcS is not a common critical component for extracellular electron transfer.

scholarly journals Advances in Synthesis of π-Extended Benzosilole Derivatives and Their Analogs

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 548
Author(s):  
Tuan Thanh Dang ◽  
Hue Minh Thi Nguyen ◽  
Hien Nguyen ◽  
Tran Ngoc Dung ◽  
Minh Tho Nguyen ◽  
...  
Keyword(s):  
Solar Cells ◽  
Physical Properties ◽  
Electronic Materials ◽  
Advanced Materials ◽  
Potential Applications

Benzosiloles and their π-extended derivatives are present in many important advanced materials due to their excellent physical properties. Especially, they have found many potential applications in the development of novel electronic materials such as OLEDs, semiconductors and solar cells. In this review, we have summarized several main approaches to construct (di)benzosilole derivatives and (benzo)siloles fused to aromatic five- and six-membered heterocycles.

Photo-induced variation of magnetism in coordination polymers with ligand-based electron transfer

2021 ◽  
Author(s):  
Yan-Lei Lu ◽  
Wen-Long Lan ◽  
Wei Shi ◽  
Qionghua Jin ◽  
Peng Cheng
Keyword(s):  
Electron Transfer ◽  
Coordination Polymers ◽  
Optical Memory ◽  
High Density ◽  
Information Storage ◽  
Memory Devices ◽  
Storage Materials ◽  
Potential Applications ◽  
Induced Variation

Photo-induced variation of magnetism from ligand-based electron transfer have been extensively studied because of their potential applications in magneto-optical memory devices, light-responsive switches, and high-density information storage materials. In this...

scholarly journals Efficient long-range conduction in cable bacteria through nickel protein wires

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Henricus T. S. Boschker ◽  
Perran L. M. Cook ◽  
Lubos Polerecky ◽  
Raghavendran Thiruvallur Eachambadi ◽  
Helena Lozano ◽  
...  
Keyword(s):  
Electron Transport ◽  
Long Range ◽  
Cell Envelope ◽  
Protein Structures ◽  
Chemical Imaging ◽  
Electrical Currents ◽  
Core Proteins ◽  
Active Metal ◽  
Unknown Form ◽  
High Resolution Microscopy

AbstractFilamentous cable bacteria display long-range electron transport, generating electrical currents over centimeter distances through a highly ordered network of fibers embedded in their cell envelope. The conductivity of these periplasmic wires is exceptionally high for a biological material, but their chemical structure and underlying electron transport mechanism remain unresolved. Here, we combine high-resolution microscopy, spectroscopy, and chemical imaging on individual cable bacterium filaments to demonstrate that the periplasmic wires consist of a conductive protein core surrounded by an insulating protein shell layer. The core proteins contain a sulfur-ligated nickel cofactor, and conductivity decreases when nickel is oxidized or selectively removed. The involvement of nickel as the active metal in biological conduction is remarkable, and suggests a hitherto unknown form of electron transport that enables efficient conduction in centimeter-long protein structures.

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