Electrochemical insight into the mechanism of electron transport in biofilms of Geobacter sulfurreducens

2011 ◽  
Vol 56 (28) ◽  
pp. 10791-10795 ◽  
Author(s):  
Germán D. Schrott ◽  
P. Sebastian Bonanni ◽  
Luciana Robuschi ◽  
Abraham Esteve-Nuñez ◽  
Juan Pablo Busalmen
Keyword(s):  
Electron Transport ◽  
Geobacter Sulfurreducens ◽  
Insight Into

scholarly journals Spatially Resolved Electron Transport through Anode‐Respiring Geobacter sulfurreducens Biofilms: Controls and Constraints

2021 ◽  
Author(s):  
Xiaojia He ◽  
Grayson Chadwick ◽  
Fernanda Jiménez Otero ◽  
Victoria Orphan ◽  
Christof Meile
Keyword(s):  
Electron Transport ◽  
Geobacter Sulfurreducens ◽  
Spatially Resolved

scholarly journals Spatially Resolved Electron Transport through Anode‐Respiring Geobacter sulfurreducens Biofilms: Controls and Constraints

2021 ◽  
Author(s):  
Xiaojia He ◽  
Grayson Chadwick ◽  
Fernanda Jiménez Otero ◽  
Victoria Orphan ◽  
Christof Meile
Keyword(s):  
Electron Transport ◽  
Geobacter Sulfurreducens ◽  
Spatially Resolved

scholarly journals Aromatic Amino Acids Required for Pili Conductivity and Long-Range Extracellular Electron Transport in Geobacter sulfurreducens

mBio ◽  
2013 ◽  
Vol 4 (2) ◽  
Author(s):  
Madeline Vargas ◽  
Nikhil S. Malvankar ◽  
Pier-Luc Tremblay ◽  
Ching Leang ◽  
Jessica A. Smith ◽  
...  
Keyword(s):  
Amino Acids ◽  
Electron Transport ◽  
Long Range ◽  
Microbial Fuel Cells ◽  
Aromatic Amino Acids ◽  
Geobacter Sulfurreducens ◽  
Control Strain ◽  
Content Type ◽  
Current Production ◽  
Extracellular Electron Transport

ABSTRACTIt has been proposed thatGeobacter sulfurreducensrequires 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 ofG. 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 whichG. sulfurreducensPilA 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 multihemec-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 ofG. sulfurreducensmust be conductive in order for the cells to be effective in extracellular long-range electron transport.IMPORTANCEExtracellular electron transfer byGeobacterspecies 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, andGeobacterorganisms are often abundant in such environments.Geobacter sulfurreducensproduces 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 ofG. sulfurreducensthat produces pili with low conductivity is limited in these extracellular electron transport functions provides further insight into these environmentally significant processes.

Long-range electron transport to Fe(III) oxide via pili with metallic-like conductivity

2012 ◽  
Vol 40 (6) ◽  
pp. 1186-1190 ◽  
Author(s):  
Derek R. Lovley
Keyword(s):  
Electron Transport ◽  
Long Range ◽  
Geobacter Sulfurreducens ◽  
Oxide Reduction ◽  
Electron Hopping ◽  
Electrically Conductive ◽  
Electron Conduction ◽  
Geobacter Species ◽  
Redox Active

The mechanisms for Fe(III) oxide reduction by Geobacter species are of interest because Geobacter species have been shown to play an important role in Fe(III) oxide reduction in a diversity of environments in which Fe(III) reduction is a geochemically significant process. Geobacter species specifically express pili during growth on Fe(III) oxide compared with growth on soluble chelated Fe(III), and mutants that cannot produce pili are unable to effectively reduce Fe(III) oxide. The pili of Geobacter sulfurreducens are electrically conductive along their length under physiologically relevant conditions and exhibit a metallic-like conductivity similar to that observed previously in synthetic organic metals. Metallic-like conductivity in a biological protein filament is a previously unrecognized mechanism for electron transport that differs significantly from the more well-known biological strategy of electron hopping/tunnelling between closely spaced redox-active proteins. The multihaem c-type cytochrome OmcS is specifically associated with pili and is necessary for Fe(III) oxide reduction. However, multiple lines of evidence, including the metallic-like conductivity of the pili and the fact that OmcS molecules are spaced too far apart for electron hopping/tunnelling, indicate that OmcS is not responsible for long-range electron conduction along the pili. The role of OmcS may be to facilitate electron transfer from the pili to Fe(III) oxide. Long-range electron transport via pili with metallic-like conductivity is a paradigm shift that has important implications not only for Fe(III) oxide reduction, but also for interspecies electron exchange in syntrophic microbial communities as well as microbe–electrode interactions and the emerging field of bioelectronics.

Inhibition of Photosynthetic Electron Transport by Azaphenanthrenes

1974 ◽  
Vol 29 (9-10) ◽  
pp. 545-551 ◽  
Author(s):  
Walter Oettmeier ◽  
Rolf Grewe
Keyword(s):  
Electron Transport ◽  
Mechanism Of Action ◽  
Inhibitory Activity ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Iron Complexes ◽  
Lower Activity ◽  
Photosynthetic Electron Flow ◽  
Isolated Chloroplasts ◽  
Insight Into

Abstract Various mono-and diazaphenanthrenes were prepared and assayed for their activity as inhibi­tors of photosynthetic electron flow in isolated chloroplasts in order to get more insight into the mechanism of action of the well known inhibitor o-phenanthroline = 1,10-diazaphenanthrene. The results show that 1-, 4-and 5-azaphenanthrene are only slightly less active than 1,10-diazaphen-anthrene. In the case of the different diazaphenanthrenes, 1,4-, 1,7-and 5,6-diazaphenanthrene exhibited somewhat lower activity than 1,10-diaphenanthrene, whereas 2,9-and 4,7-diazaphen-anthrene were completely inactive. Substitution at C-atoms of 1,10-diazaphenanthrene leads to an increase in activity in the case of the 4-and 7-position, regardless of electropositive or electro­ negative substituents, whereas substitution at the 2-, 3-, 5-, 6-, 8-and 9-position leads to a de­ creased activity. The ability of 1,10-diazaphenanthrene to form iron complexes seems to be of little relevance to the inhibitory activity on photosynthetic electron transport. This follows also from the fact that other strong iron complexing agens, like 2.2'-bipyridine or 8-hydroxyquinoline, are not inhibitory

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.

Application of electrochemical surface plasmon resonance (ESPR) to the study of electroactive microbial biofilms

2018 ◽  
Vol 20 (40) ◽  
pp. 25648-25656 ◽  
Author(s):  
Joel Golden ◽  
Matthew D. Yates ◽  
Michelle Halsted ◽  
Leonard Tender
Keyword(s):  
Surface Plasmon Resonance ◽  
Electron Transport ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Electrode Surface ◽  
Geobacter Sulfurreducens ◽  
Microbial Biofilms ◽  
Electrode Interface ◽  
Extracellular Electron Transport

Results reveal that for an electrode-grown Geobacter sulfurreducens biofilm, as much as 70% of cytochrome hemes residing within hundreds of nanometers from the electrode surface store electrons even as extracellular electron transport is occurring across the biofilm/electrode interface.

scholarly journals Simulation of electron transport during electron-beam-induced deposition of nanostructures

2013 ◽  
Vol 4 ◽  
pp. 781-792 ◽  
Author(s):  
Francesc Salvat-Pujol ◽  
Harald O Jeschke ◽  
Roser Valentí
Keyword(s):  
Electron Beam ◽  
Electron Transport ◽  
Radiation Transport ◽  
Secondary Electrons ◽  
Electron Trajectories ◽  
Backscattered Electrons ◽  
Multi Scale ◽  
Different Depths ◽  
Electron Beam Induced Deposition ◽  
Insight Into

We present a numerical investigation of energy and charge distributions during electron-beam-induced growth of tungsten nanostructures on SiO2 substrates by using a Monte Carlo simulation of the electron transport. This study gives a quantitative insight into the deposition of energy and charge in the substrate and in the already existing metallic nanostructures in the presence of the electron beam. We analyze electron trajectories, inelastic mean free paths, and the distribution of backscattered electrons in different compositions and at different depths of the deposit. We find that, while in the early stages of the nanostructure growth a significant fraction of electron trajectories still interacts with the substrate, when the nanostructure becomes thicker the transport takes place almost exclusively in the nanostructure. In particular, a larger deposit density leads to enhanced electron backscattering. This work shows how mesoscopic radiation-transport techniques can contribute to a model that addresses the multi-scale nature of the electron-beam-induced deposition (EBID) process. Furthermore, similar simulations can help to understand the role that is played by backscattered electrons and emitted secondary electrons in the change of structural properties of nanostructured materials during post-growth electron-beam treatments.

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