scholarly journals Uptake of self-secreted flavins as bound cofactors for extracellular electron transfer in Geobacter species

2014 ◽  
Vol 7 (4) ◽  
pp. 1357-1361 ◽  
Author(s):  
Akihiro Okamoto ◽  
Koichiro Saito ◽  
Kengo Inoue ◽  
Kenneth H. Nealson ◽  
Kazuhito Hashimoto ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Outer Membrane ◽  
Extracellular Electron Transfer ◽  
Geobacter Species

Geobacter cells utilize self-secreted riboflavin as a bound-cofactor in outer-membrane c-type cytochromes to enhance the rate of bacterial electron transport.

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 Tracking Electron Uptake from a Cathode into Shewanella Cells: Implications for Energy Acquisition from Solid-Substrate Electron Donors

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Annette R. Rowe ◽  
Pournami Rajeev ◽  
Abhiney Jain ◽  
Sahand Pirbadian ◽  
Akihiro Okamoto ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Complex I ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Extracellular Electron Transfer ◽  
Terminal Electron Acceptor ◽  
Cellular Energy ◽  
Transport Chain ◽  
Energy Acquisition

ABSTRACTWhile typically investigated as a microorganism capable of extracellular electron transfer to minerals or anodes,Shewanella oneidensisMR-1 can also facilitate electron flow from a cathode to terminal electron acceptors, such as fumarate or oxygen, thereby providing a model system for a process that has significant environmental and technological implications. This work demonstrates that cathodic electrons enter the electron transport chain ofS. oneidensiswhen oxygen is used as the terminal electron acceptor. The effect of electron transport chain inhibitors suggested that a proton gradient is generated during cathode oxidation, consistent with the higher cellular ATP levels measured in cathode-respiring cells than in controls. Cathode oxidation also correlated with an increase in the cellular redox (NADH/FMNH2) pool determined with a bioluminescence assay, a proton uncoupler, and a mutant of proton-pumping NADH oxidase complex I. This work suggested that the generation of NADH/FMNH2under cathodic conditions was linked to reverse electron flow mediated by complex I. A decrease in cathodic electron uptake was observed in various mutant strains, including those lacking the extracellular electron transfer components necessary for anodic-current generation. While no cell growth was observed under these conditions, here we show that cathode oxidation is linked to cellular energy acquisition, resulting in a quantifiable reduction in the cellular decay rate. This work highlights a potential mechanism for cell survival and/or persistence on cathodes, which might extend to environments where growth and division are severely limited.IMPORTANCEThe majority of our knowledge of the physiology of extracellular electron transfer derives from studies of electrons moving to the exterior of the cell. The physiological mechanisms and/or consequences of the reverse processes are largely uncharacterized. This report demonstrates that when coupled to oxygen reduction, electrode oxidation can result in cellular energy acquisition. This respiratory process has potentially important implications for how microorganisms persist in energy-limited environments, such as reduced sediments under changing redox conditions. From an applied perspective, this work has important implications for microbially catalyzed processes on electrodes, particularly with regard to understanding models of cellular conversion of electrons from cathodes to microbially synthesized products.

scholarly journals His/Met heme ligation in the PioA outer membrane cytochrome enabling light-driven extracellular electron transfer by Rhodopseudomonas palustris TIE-1

2020 ◽  
Vol 31 (35) ◽  
pp. 354002
Author(s):  
Dao-Bo Li ◽  
Marcus J Edwards ◽  
Anthony W Blake ◽  
Simone E Newton-Payne ◽  
Samuel E H Piper ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Rhodopseudomonas Palustris ◽  
Extracellular Electron Transfer ◽  
Heme Ligation

The roles of outer membrane cytochromes ofShewanellaandGeobacterin extracellular electron transfer

2009 ◽  
Vol 1 (4) ◽  
pp. 220-227 ◽  
Author(s):  
Liang Shi ◽  
David J. Richardson ◽  
Zheming Wang ◽  
Sebastien N. Kerisit ◽  
Kevin M. Rosso ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Extracellular Electron Transfer

scholarly journals Shewanella oneidensis as a living electrode for controlled radical polymerization

2018 ◽  
Vol 115 (18) ◽  
pp. 4559-4564 ◽  
Author(s):  
Gang Fan ◽  
Christopher M. Dundas ◽  
Austin J. Graham ◽  
Nathaniel A. Lynd ◽  
Benjamin K. Keitz
Keyword(s):  
Electron Transfer ◽  
Metabolic Engineering ◽  
Electron Transport ◽  
Radical Polymerization ◽  
Copper Catalyst ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Metal Catalyst ◽  
General Strategy ◽  
Significant Activity

Metabolic engineering has facilitated the production of pharmaceuticals, fuels, and soft materials but is generally limited to optimizing well-defined metabolic pathways. We hypothesized that the reaction space available to metabolic engineering could be expanded by coupling extracellular electron transfer to the performance of an exogenous redox-active metal catalyst. Here we demonstrate that the electroactive bacterium Shewanella oneidensis can control the activity of a copper catalyst in atom-transfer radical polymerization (ATRP) via extracellular electron transfer. Using S. oneidensis, we achieved precise control over the molecular weight and polydispersity of a bioorthogonal polymer while similar organisms, such as Escherichia coli, showed no significant activity. We found that catalyst performance was a strong function of bacterial metabolism and specific electron transport proteins, both of which offer potential biological targets for future applications. Overall, our results suggest that manipulating extracellular electron transport pathways may be a general strategy for incorporating organometallic catalysis into the repertoire of metabolically controlled transformations.

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