scholarly journals Vanadium(V) Reduction by Shewanella oneidensis MR-1 Requires Menaquinone and Cytochromes from the Cytoplasmic and Outer Membranes

2004 ◽  
Vol 70 (3) ◽  
pp. 1405-1412 ◽  
Author(s):  
Judith M. Myers ◽  
William E. Antholine ◽  
Charles R. Myers
Keyword(s):  
Electron Transport ◽  
Shewanella Oneidensis ◽  
Anaerobic Growth ◽  
Metal Species ◽  
Resonance Spectroscopy ◽  
Transport Chain ◽  
Respiratory Plasticity ◽  
Cell Components ◽  
Tetraheme Cytochrome ◽  
Membrane Components

ABSTRACT The metal-reducing bacterium Shewanella oneidensis MR-1 displays remarkable anaerobic respiratory plasticity, which is reflected in the extensive number of electron transport components encoded in its genome. In these studies, several cell components required for the reduction of vanadium(V) were determined. V(V) reduction is mediated by an electron transport chain which includes cytoplasmic membrane components (menaquinone and the tetraheme cytochrome CymA) and the outer membrane (OM) cytochrome OmcB. A partial role for the OM cytochrome OmcA was evident. Electron spin resonance spectroscopy demonstrated that V(V) was reduced to V(IV). V(V) reduction did not support anaerobic growth. This is the first report delineating specific electron transport components that are required for V(V) reduction and of a role for OM cytochromes in the reduction of a soluble metal species.

scholarly journals Investigation of the Electron Transport Chain to and the Catalytic Activity of the Diheme CytochromecPeroxidase CcpA of Shewanella oneidensis

2011 ◽  
Vol 77 (17) ◽  
pp. 6172-6180 ◽  
Author(s):  
Björn Schütz ◽  
Julian Seidel ◽  
Gunnar Sturm ◽  
Oliver Einsle ◽  
Johannes Gescher
Keyword(s):  
Electron Transport ◽  
Peroxidase Activity ◽  
Electron Transport Chain ◽  
Ferric Iron ◽  
Shewanella Oneidensis ◽  
Selective Advantage ◽  
Competitive Growth ◽  
Content Type ◽  
Transport Chain

ABSTRACTBacterial dihemec-type cytochrome peroxidases (BCCPs) catalyze the periplasmic reduction of hydrogen peroxide to water. The gammaproteobacteriumShewanella oneidensisproduces the peroxidase CcpA under a number of anaerobic conditions, including dissimilatory iron-reducing conditions. We wanted to understand the function of this protein in the organism and its putative connection to the electron transport chain to ferric iron. CcpA was isolated and tested for peroxidase activity, and its structural conformation was analyzed by X-ray crystallography. CcpA exhibitedin vitroperoxidase activity and had a structure typical of diheme peroxidases. It was produced in almost equal amounts under anaerobic and microaerophilic conditions. With 50 mM ferric citrate and 50 μM oxygen in the growth medium, CcpA expression results in a strong selective advantage for the cell, which was detected in competitive growth experiments with wild-type and ΔccpAmutant cells that lack the entireccpAgene due to a markerless deletion. We were unable to reduce CcpA directly with CymA, MtrA, or FccA, which are known key players in the chain of electron transport to ferric iron and fumarate but identified the small monoheme ScyA as a mediator of electron transport between CymA and BCCP. To our knowledge, this is the first detailed description of a complete chain of electron transport to a periplasmicc-type cytochrome peroxidase. This study furthermore reports the possibility of establishing a specific electron transport chain usingc-type cytochromes.

scholarly journals The ultrastructure of Shewanella oneidensis MR-1 nanowires revealed by electron cryo-tomography

2017 ◽  
Author(s):  
Poorna Subramanian ◽  
Sahand Pirbadian ◽  
Mohamed Y. El-Naggar ◽  
Grant J. Jensen
Keyword(s):  
Electron Transport ◽  
Outer Membrane ◽  
Solid Phase ◽  
Outer Membrane Proteins ◽  
Light And Electron Microscopy ◽  
Shewanella Oneidensis ◽  
Transport Chain ◽  
High Resolution Images ◽  
Micrometer Scale

Abstract:Bacterial nanowires have garnered recent interest as a proposed Extracellular Electron Transfer (EET) pathway that links the bacterial electron transport chain to solid-phase electron acceptors away from the cell. In vivofluorescence Light Microscopy (fLM) imaging recently showed that Shewanella oneidensis MR-1 nanowires are extensions of the outer membrane that contain EET components. However, their fine structure and distribution of cytochrome electron carriers remained unclear, making it difficult to evaluate the electron transport mechanism along the nanowires. Here, we report high-resolution images of nanowires using Electron Cryo-Tomography (ECT). We developed a robust method for fLM imaging of nanowire growth on electron microscopy grids and used correlative light and electron microscopy to identify and image the same nanowires by ECT. Our results confirm that S. oneidensis nanowires are outer membrane extensions, and further reveal that nanowires are dynamic chains of interconnected Outer Membrane Vesicles (OMVs) with variable dimensions, curvature, and extent of tubulation. Junction densities that potentially stabilize OMV chains are seen between neighboring vesicles in cryotomograms. Our ECT results also provide the first hints of the positions and packing of periplasmic and outer membrane proteins consistent with cytochromes. We observe tight packing of putative cytochromes along lateral patches that extend tens of nanometers, but not across the micrometer scale of whole nanowires. We therefore propose that electron transfer along nanowires involves a combination of direct hopping and diffusive events that link neighboring redox proteins.

scholarly journals AB0031 T HELPER 17 CELLS WERE SIGNIFICANTLY DECREASED BY MITOCHONDRIAL ELECTRON TRANSPORT CHAIN COMPLEX INHIBITOR IN PATIENTS WITH RHEUMATOID ARTHRITIS

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1318.2-1318
Author(s):  
H. R. Lee ◽  
S. J. Yoo ◽  
J. Kim ◽  
I. S. Yoo ◽  
C. K. Park ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Electron Transport ◽  
Disease Activity ◽  
Th17 Cells ◽  
Electron Transport Chain ◽  
Chain Complex ◽  
Complex Iii ◽  
Mitochondrial Electron Transport Chain ◽  
Transport Chain ◽  
Healthy Control

Background:Reactive oxygen species (ROS) and T helper 17 (TH17) cells have been known to play an important role in the pathogenesis of rheumatoid arthritis (RA). However, the interrelationship between ROS and TH17 remains unclear in RAObjectives:To explore whether ROS affect TH17 cells in peripheral blood mononuclear cells (PBMC) of RA patients, we analyzed ROS expressions among T cell subsets following treatment with mitochondrial electron transport chain complex inhibitors.Methods:Blood samples were collected from 40 RA patients and 10 healthy adult volunteers. RA activity was divided according to clinical parameter DAS28. PBMC cells were obtained from the whole blood using lymphocyte separation medium density gradient centrifugation. Following PBMC was stained with Live/Dead stain dye, cells were incubated with antibodies for CD3, CD4, CD8, and CD25. After fixation and permeabilization, samples were stained with antibodies for FoxP3 and IL-17A. MitoSox were used for mitochondrial specific staining.Results:The frequency of TH17 cells was increased by 4.83 folds in moderate disease activity group (5.1>DAS28≥3.2) of RA patients compared to healthy control. Moderate RA activity patients also showed higher ratio of TH17/Treg than healthy control (3.57 folds). All RA patients had elevated expression of mitochondrial specific ROS than healthy control. When PBMC cells were treated with 2.5uM of antimycin A (mitochondrial electron transport chain complex III inhibitor) for 16 h, the frequency of TH17 cells was significantly decreased.Conclusion:The mitochondrial electron transport chain complex III inhibitor markedly downregulated the frequency of TH17 cells in moderate disease activity patients with RA. These findings provide a novel approach to regulate TH17 function in RA through mitochondrial metabolism related ROS production.References:[1]Szekanecz, Z., et al., New insights in synovial angiogenesis. Joint Bone Spine, 2010. 77(1): p. 13-9.[2]Prevoo, M.L., et al., Modified disease activity scores that include twenty-eight-joint counts. Development and validation in a prospective longitudinal study of patients with rheumatoid arthritis. Arthritis Rheum, 1995. 38(1): p. 44-8.Disclosure of Interests:None declared

scholarly journals Effects of Different Planting Densities on Photosynthesis in Maize Determined via Prompt Fluorescence, Delayed Fluorescence and P700 Signals

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 276
Author(s):  
Wanying Chen ◽  
Bo Jia ◽  
Junyu Chen ◽  
Yujiao Feng ◽  
Yue Li ◽  
...  
Keyword(s):  
Electron Transport ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Electron Transport Chain ◽  
Plant Density ◽  
Photosynthetic Electron Transport ◽  
Planting Density ◽  
Strong Impact ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

The mutual shading among individual field-grown maize plants resulting from high planting density inevitably reduces leaf photosynthesis, while regulating the photosynthetic transport chain has a strong impact on photosynthesis. However, the effect of high planting density on the photosynthetic electron transport chain in maize currently remains unclear. In this study, we simultaneously measured prompt chlorophyll a fluorescence (PF), modulated 820 nm reflection (MR) and delayed chlorophyll a fluorescence (DF) in order to investigate the effect of high planting density on the photosynthetic electron transport chain in two maize hybrids widely grown in China. PF transients demonstrated a gradual reduction in their signal amplitude with increasing planting density. In addition, high planting density induced positive J-step and G-bands of the PF transients, reduced the values of PF parameters PIABS, RC/CSO, TRO/ABS, ETO/TRO and REO/ETO, and enhanced ABS/RC and N. MR kinetics showed an increase of their lowest point with increasing high planting density, and thus the values of MR parameters VPSI and VPSII-PSI were reduced. The shapes of DF induction and decay curves were changed by high planting density. In addition, high planting density reduced the values of DF parameters I1, I2, L1 and L2, and enhanced I2/I1. These results suggested that high planting density caused harm on multiple components of maize photosynthetic electron transport chain, including an inactivation of PSII RCs, a blocked electron transfer between QA and QB, a reduction in PSI oxidation and re-reduction activities, and an impaired PSI acceptor side. Moreover, a comparison between PSII and PSI activities demonstrated the greater effect of plant density on the former.

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