scholarly journals Tracking electron uptake from a cathode intoShewanellacells: implications for generating maintenance energy from solid substrates

2017 ◽  
Author(s):  
Annette R. Rowe ◽  
Pournami Rajeev ◽  
Abhiney Jain ◽  
Sahand Pirbadian ◽  
Akihiro Okamotao ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Nadh Oxidase ◽  
Electron Flow ◽  
Proton Pumping ◽  
Model Systems ◽  
Extracellular Electron Transfer ◽  
Terminal Electron Acceptor ◽  
Transport Chain

While 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 systems for a process that has significant environmental and technological implications. This work demonstrates that cathodic electrons enter the electron transport chain of S.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 relative to controls. Cathode oxidation also correlated with an increase in the cellular redox (NADH/FMNH2) pool using a bioluminescent assay. Using a proton uncoupler, generation of NADH/FMNH2under cathodic conditions was linked to reverse electron flow mediated by the proton pumping NADH oxidase 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 conservation, resulting in a quantifiable reduction in cellular decay rate. This work highlights a potential mechanism for cell survival and/or persistence in environments where growth and division are severely limited.

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 Cytochrome c550 from Pseudomonas aeruginosa

1993 ◽  
Vol 289 (1) ◽  
pp. 173-178 ◽  
Author(s):  
P Reichmann ◽  
H Görisch
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Electron Transfer ◽  
Oxygen Consumption ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Prosthetic Group ◽  
Midpoint Potential ◽  
Transport Chain ◽  
Ethanol Dehydrogenase ◽  
Soluble C

In cells of Pseudomonas aeruginosa A.T.C.C. 17933 grown on ethanol the synthesis of a soluble c-type cytochrome, together with quinoprotein ethanol dehydrogenase, is induced. The cytochrome, with an alpha-absorption band at 550 nm, was purified to homogeneity. The molecular mass of the monomeric protein is 15 kDa, the pI is 4.8, and it contains one haem prosthetic group. The midpoint potential of the autoxidizable, but not autoreducible, cytochrome is 280 mV. Cytochrome c550 mediates electron transfer between quinoprotein ethanol dehydrogenase and ferricyanide. In a system composed of membrane particles with NN‘NN’-tetramethyl-p-phenylenediamine oxidase activity and quinoprotein ethanol dehydrogenase, oxygen consumption is only observed in the presence of cytochrome c550. This indicates the participation of the cytochrome in the electron-transport chain linked to quinoprotein ethanol dehydrogenase in P. aeruginosa. The electron transport from ethanol dehydrogenase to oxygen is inhibited by myxothiazol and antimycin, indicating that a cytochrome bc1-like complex is involved.

Rewiring photosynthesis: a photosystem I-hydrogenase chimera that makes H2in vivo

2020 ◽  
Vol 13 (9) ◽  
pp. 2903-2914 ◽  
Author(s):  
Andrey Kanygin ◽  
Yuval Milrad ◽  
Chandrasekhar Thummala ◽  
Kiera Reifschneider ◽  
Patricia Baker ◽  
...  
Keyword(s):  
Electron Transport ◽  
Hydrogen Production ◽  
Photosystem I ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

Photosystem I-hydrogenase chimera intercepts electron flow directly from the photosynthetic electron transport chain and directs it to hydrogen production.

scholarly journals Purification of Helicobacter pylori NCTC 11637 Cytochrome bc1 and Respiration with d-Proline as a Substrate

2009 ◽  
Vol 192 (5) ◽  
pp. 1410-1415 ◽  
Author(s):  
Minoru Tanigawa ◽  
Tomomitsu Shinohara ◽  
Katsushi Nishimura ◽  
Kumiko Nagata ◽  
Morio Ishizuka ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Amino Acid ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Gene Clusters ◽  
Acid Dehydrogenase ◽  
Amino Acid Dehydrogenase ◽  
Transport Chain ◽  
H Pylori

ABSTRACT Helicobacter pylori is a microaerophilic bacterium associated with gastric inflammation and peptic ulcers. Knowledge of how pathogenic organisms produce energy is important from a therapeutic point of view. We found d-amino acid dehydrogenase-mediated electron transport from d-proline or d-alanine to oxygen via the respiratory chain in H. pylori. Coupling of the electron transport to ATP synthesis was confirmed by using uncoupler reagents. We reconstituted the electron transport chain to demonstrate the electron flow from the d-amino acids to oxygen using the recombinant cytochrome bc 1 complex, cytochrome c-553, and the terminal oxidase cytochrome cbb 3 complex. Upon addition of the recombinant d-amino acid dehydrogenase and d-proline or d-alanine to the reconstituted electron transport system, reduction of cytochrome cbb 3 and oxygen consumption was revealed spectrophotometrically and polarographically, respectively. Among the constituents of H. pylori's electron transport chain, only the cytochrome bc 1 complex had been remained unpurified. Therefore, we cloned and sequenced the H. pylori NCTC 11637 cytochrome bc 1 gene clusters encoding Rieske Fe-S protein, cytochrome b, and cytochrome c 1, with calculated molecular masses of 18 kDa, 47 kDa, and 32 kDa, respectively, and purified the recombinant monomeric protein complex with a molecular mass of 110 kDa by gel filtration. The absorption spectrum of the recombinant cytochrome bc 1 complex showed an α peak at 561 nm with a shoulder at 552 nm.

scholarly journals Experimental conditions affect the site of tetrazolium violet reduction in the electron transport chain of Lactococcus lactis

Microbiology ◽  
2009 ◽  
Vol 155 (9) ◽  
pp. 2941-2948 ◽  
Author(s):  
Sybille Tachon ◽  
Damien Michelon ◽  
Emilie Chambellon ◽  
Monique Cantonnet ◽  
Christine Mezange ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Lactococcus Lactis ◽  
Electron Transport Chain ◽  
Experimental Conditions ◽  
Plate Test ◽  
Tetrazolium Salts ◽  
Transport Chain ◽  
Reduction Mechanisms ◽  
Tetrazolium Violet

The reduction of tetrazolium salts to coloured formazans is often used as an indicator of cell metabolism during microbiology studies, although the reduction mechanisms have never clearly been established in bacteria. The objective of the present study was to identify the reduction mechanisms of tetrazolium violet (TV) in Lactococcus lactis using a mutagenesis approach, under two experimental conditions generally applied in microbiology: a plate test with growing cells, and a liquid test with non-growing (resting) cells. The results showed that in both tests, TV reduction resulted from electron transfer from an intracellular donor (mainly NADH) to TV via the electron transport chain (ETC), but the reduction sites in the ETC depended on experimental conditions. Using the plate test, menaquinones were essential for TV reduction and membrane NADH dehydrogenases (NoxA and/or NoxB) were partly involved in electron transfer to menaquinones. In this case, TV reduction mainly occurred outside the cells and in the outer part of the plasma membrane. During the liquid test, TV was directly reduced by NoxA and/or NoxB, probably in the inner part of the membrane, where NoxA and NoxB are localized. In this case, reduction was directly related to the intracellular NADH pool. Based on these findings, new applications for TV tests are proposed, such as NADH pool determination with the liquid test and the screening of mutants affected in menaquinone biosynthesis with the plate test. Preliminary results using other tetrazolium salts in the plate test showed that the reduction sites depended on the salt, suggesting that similar studies should be carried out with other tetrazolium salts so that the outcome of each test can be interpreted correctly.

The efficiency and plasticity of mitochondrial energy transduction

2005 ◽  
Vol 33 (5) ◽  
pp. 897-904 ◽  
Author(s):  
M.D. Brand
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Uncoupling Protein ◽  
Coupling Efficiency ◽  
Energy Transduction ◽  
Proton Pumping ◽  
Complex Iii ◽  
Proton Pumps ◽  
Transport Chain

Since it was first realized that biological energy transduction involves oxygen and ATP, opinions about the amount of ATP made per oxygen consumed have continually evolved. The coupling efficiency is crucial because it constrains mechanistic models of the electron-transport chain and ATP synthase, and underpins the physiology and ecology of how organisms prosper in a thermodynamically hostile environment. Mechanistically, we have a good model of proton pumping by complex III of the electron-transport chain and a reasonable understanding of complex IV and the ATP synthase, but remain ignorant about complex I. Energy transduction is plastic: coupling efficiency can vary. Whether this occurs physiologically by molecular slipping in the proton pumps remains controversial. However, the membrane clearly leaks protons, decreasing the energy funnelled into ATP synthesis. Up to 20% of the basal metabolic rate may be used to drive this basal leak. In addition, UCP1 (uncoupling protein 1) is used in specialized tissues to uncouple oxidative phosphorylation, causing adaptive thermogenesis. Other UCPs can also uncouple, but are tightly regulated; they may function to decrease coupling efficiency and so attenuate mitochondrial radical production. UCPs may also integrate inputs from different fuels in pancreatic β-cells and modulate insulin secretion. They are exciting potential targets for treatment of obesity, cachexia, aging and diabetes.

scholarly journals Oncogenic pathways and the electron transport chain: a dangeROS liaison

2019 ◽  
Vol 122 (2) ◽  
pp. 168-181 ◽  
Author(s):  
Vittoria Raimondi ◽  
Francesco Ciccarese ◽  
Vincenzo Ciminale
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Second Messengers ◽  
Driver Mutations ◽  
Cell Phenotype ◽  
Oxygen Species ◽  
Hallmarks Of Cancer ◽  
Oncogenic Pathways ◽  
Transport Chain

AbstractDriver mutations in oncogenic pathways, rewiring of cellular metabolism and altered ROS homoeostasis are intimately connected hallmarks of cancer. Electrons derived from different metabolic processes are channelled into the mitochondrial electron transport chain (ETC) to fuel the oxidative phosphorylation process. Electrons leaking from the ETC can prematurely react with oxygen, resulting in the generation of reactive oxygen species (ROS). Several signalling pathways are affected by ROS, which act as second messengers controlling cell proliferation and survival. On the other hand, oncogenic pathways hijack the ETC, enhancing its ROS-producing capacity by increasing electron flow or by impinging on the structure and organisation of the ETC. In this review, we focus on the ETC as a source of ROS and its modulation by oncogenic pathways, which generates a vicious cycle that resets ROS levels to a higher homoeostatic set point, sustaining the cancer cell phenotype.

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