Antibody Recognition Force Microscopy Shows that Outer Membrane Cytochromes OmcA and MtrC Are Expressed on the Exterior Surface of Shewanella oneidensis MR-1

Multiheme cytochromes, located on the bacterial cell surface, function as long-distance (> 10 nm) electron conduits linking intracellular reactions to external surfaces. This extracellular electron transfer process, which allows microorganisms to gain energy by respiring solid redox-active minerals, also facilitates the wiring of cells to electrodes. While recent studies suggested that a chiral induced spin selectivity effect is linked to efficient electron transmission through biomolecules, this phenomenon has not been investigated in the extracellular electron conduits. Using magnetic conductive probe atomic force microscopy, Hall voltage measurements, and spin-dependent electrochemistry of the decaheme cytochromes MtrF and OmcA from the metal-reducing bacterium <i>Shewanella oneidensis</i> MR-1, we show that electron transport through these extracellular conduits is spin-selective. Our study has implications for understanding how spin-dependent interactions and magnetic fields may control electron transport across biotic-abiotic interfaces in both natural and biotechnological systems.

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Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1

Applied and Environmental Microbiology ◽

10.1128/aem.00022-09 ◽

2009 ◽

Vol 75 (11) ◽

pp. 3641-3647 ◽

Cited By ~ 44

Author(s):

Gary A. Icopini ◽

Joe G. Lack ◽

Larry E. Hersman ◽

Mary P. Neu ◽

Hakim Boukhalfa

Keyword(s):

Electron Acceptor ◽

Shewanella Oneidensis ◽

Cell Suspensions ◽

Reduced Form ◽

Stable Form ◽

Experimental Conditions ◽

Geobacter Metallireducens ◽

Terminal Electron Acceptor ◽

Reducing Bacteria ◽

Metal Reducing Bacteria

ABSTRACT We examined the ability of the metal-reducing bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1 to reduce Pu(VI) and Pu(V). Cell suspensions of both bacteria reduced oxidized Pu [a mixture of Pu(VI) and Pu(V)] to Pu(IV). The rate of plutonium reduction was similar to the rate of U(VI) reduction obtained under similar conditions for each bacteria. The rates of Pu(VI) and U(VI) reduction by cell suspensions of S. oneidensis were slightly higher than the rates observed with G. metallireducens. The reduced form of Pu was characterized as aggregates of nanoparticulates of Pu(IV). Transmission electron microscopy images of the solids obtained from the cultures after the reduction of Pu(VI) and Pu(V) by S. oneidensis show that the Pu precipitates have a crystalline structure. The nanoparticulates of Pu(IV) were precipitated on the surface of or within the cell walls of the bacteria. The production of Pu(III) was not observed, which indicates that Pu(IV) was the stable form of reduced Pu under these experimental conditions. Experiments examining the ability of these bacteria to use Pu(VI) as a terminal electron acceptor for growth were inconclusive. A slight increase in cell density was observed for both G. metallireducens and S. oneidensis when Pu(VI) was provided as the sole electron acceptor; however, Pu(VI) concentrations decreased similarly in both the experimental and control cultures.

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Immobilization of Antibodies on Ultraflat Polystyrene Surfaces

Clinical Chemistry ◽

10.1093/clinchem/46.9.1456 ◽

2000 ◽

Vol 46 (9) ◽

pp. 1456-1463 ◽

Cited By ~ 36

Author(s):

Weiping Qian ◽

Danfeng Yao ◽

Fang Yu ◽

Bin Xu ◽

Rong Zhou ◽

...

Keyword(s):

Hepatitis B ◽

Uniform Distribution ◽

Surface Antigen ◽

Solid Phase ◽

Physical Adsorption ◽

Hepatitis B Surface Antigen ◽

Wafer Surface ◽

Force Microscopy ◽

Immobilized Antibodies ◽

Solid Phase Immunoassay

Abstract Background: Functional antibody surfaces were prepared on ultraflat polystyrene surfaces by physical adsorption, and the uniform distribution of monoclonal antibodies against hepatitis B surface antigen (anti-HBs) on such surfaces and the presence of dense hepatitis B surface antigen (HBsAg) particles captured by immobilized antibodies were identified. Methods: A model polystyrene film was spin-coated directly onto a silicon wafer surface. Atomic force microscopy was used to directly monitor the immobilization of anti-HBs antibodies and their specific molecular interaction with HBsAg. Enzyme immunoassay was also used to characterize functional antibody surfaces. Results: A mean roughness of 2 Å for areas of 25 μm2 was produced. We found a uniform distribution of anti-HBs antibodies on ultraflat polystyrene surfaces and the presence of dense HBsAg particles bound to such anti-HBs surfaces after incubation with HBsAg. Conclusions: This study confirmed the potential of preparing dense, homogeneous, highly specific, and highly stable antibody surfaces by immobilizing antibodies on polystyrene surfaces with controlled roughness. It is expected that such biofunctional surfaces could be of interest for the development of new solid-phase immunoassay techniques and biosensor techniques.

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Global Transcriptional Profiling of Shewanella oneidensis MR-1 during Cr(VI) and U(VI) Reduction

Applied and Environmental Microbiology ◽

10.1128/aem.71.11.7453-7460.2005 ◽

2005 ◽

Vol 71 (11) ◽

pp. 7453-7460 ◽

Cited By ~ 96

Author(s):

Rizlan Bencheikh-Latmani ◽

Sarah Middleton Williams ◽

Lisa Haucke ◽

Craig S. Criddle ◽

Liyou Wu ◽

...

Keyword(s):

Electron Acceptor ◽

Dna Microarrays ◽

Solid Phase ◽

Transcriptional Profiling ◽

Large Fraction ◽

Membrane Damage ◽

Shewanella Oneidensis ◽

Transport Pathway ◽

Reducing Conditions ◽

Genes Encoding

ABSTRACT Whole-genome DNA microarrays were used to examine the gene expression profile of Shewanella oneidensis MR-1 during U(VI) and Cr(VI) reduction. The same control, cells pregrown with nitrate and incubated with no electron acceptor, was used for the two time points considered and for both metals. U(VI)-reducing conditions resulted in the upregulation (≥3-fold) of 121 genes, while 83 genes were upregulated under Cr(VI)-reducing conditions. A large fraction of the genes upregulated [34% for U(VI) and 29% for Cr(VI)] encode hypothetical proteins of unknown function. Genes encoding proteins known to reduce alternative electron acceptors [fumarate, dimethyl sulfoxide, Mn(IV), or soluble Fe(III)] were upregulated under both U(VI)- and Cr(VI)-reducing conditions. The involvement of these upregulated genes in the reduction of U(VI) and Cr(VI) was tested using mutants lacking one or several of the gene products. Mutant testing confirmed the involvement of several genes in the reduction of both metals: mtrA, mtrB, mtrC, and menC, all of which are involved in Fe(III) citrate reduction by MR-1. Genes encoding efflux pumps were upregulated under Cr(VI)- but not under U(VI)-reducing conditions. Genes encoding proteins associated with general (e.g., groL and dnaJ) and membrane (e.g., pspBC) stress were also upregulated, particularly under U(VI)-reducing conditions, pointing to membrane damage by the solid-phase reduced U(IV) and Cr(III) and/or the direct effect of the oxidized forms of the metals. This study sheds light on the multifaceted response of MR-1 to U(VI) and Cr(VI) under anaerobic conditions and suggests that the same electron transport pathway can be used for more than one electron acceptor.

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Spin-Dependent Electron Transport through Bacterial Cell Surface Multiheme Electron Conduits

10.26434/chemrxiv.9748046 ◽

2019 ◽

Author(s):

Suryakant Mishra ◽

Sahand Pirbadian ◽

Amit Kumar Mondal ◽

Moh El-Naggar ◽

Ron Naaman

Keyword(s):

Electron Transport ◽

Cell Surface ◽

Bacterial Cell ◽

Shewanella Oneidensis ◽

Extracellular Electron Transfer ◽

Long Distance ◽

Force Microscopy ◽

Bacterial Cell Surface ◽

Redox Active ◽

Gain Energy

Multiheme cytochromes, located on the bacterial cell surface, function as long-distance (> 10 nm) electron conduits linking intracellular reactions to external surfaces. This extracellular electron transfer process, which allows microorganisms to gain energy by respiring solid redox-active minerals, also facilitates the wiring of cells to electrodes. While recent studies suggested that a chiral induced spin selectivity effect is linked to efficient electron transmission through biomolecules, this phenomenon has not been investigated in the extracellular electron conduits. Using magnetic conductive probe atomic force microscopy, Hall voltage measurements, and spin-dependent electrochemistry of the decaheme cytochromes MtrF and OmcA from the metal-reducing bacterium <i>Shewanella oneidensis</i> MR-1, we show that electron transport through these extracellular conduits is spin-selective. Our study has implications for understanding how spin-dependent interactions and magnetic fields may control electron transport across biotic-abiotic interfaces in both natural and biotechnological systems.

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Plutonium(IV) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1

Applied and Environmental Microbiology ◽

10.1128/aem.00747-07 ◽

2007 ◽

Vol 73 (18) ◽

pp. 5897-5903 ◽

Cited By ~ 53

Author(s):

Hakim Boukhalfa ◽

Gary A. Icopini ◽

Sean D. Reilly ◽

Mary P. Neu

Keyword(s):

Electron Acceptor ◽

Shewanella Oneidensis ◽

Cell Suspensions ◽

Bacterial Reduction ◽

Geobacter Metallireducens ◽

Terminal Electron Acceptor ◽

Initial Concentration ◽

Solid Phases ◽

Reducing Bacteria ◽

Metal Reducing Bacteria

ABSTRACT The bacterial reduction of actinides has been suggested as a possible remedial strategy for actinide-contaminated environments, and the bacterial reduction of Pu(VI/V) has the potential to produce highly insoluble Pu(IV) solid phases. However, the behavior of plutonium with regard to bacterial reduction is more complex than for other actinides because it is possible for Pu(IV) to be further reduced to Pu(III), which is relatively more soluble than Pu(IV). This work investigates the ability of the metal-reducing bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1 to enzymatically reduce freshly precipitated amorphous Pu(IV) (OH)4 [Pu(IV)(OH)4(am)] and soluble Pu(IV)(EDTA). In cell suspensions without added complexing ligands, minor Pu(III) production was observed in cultures containing S. oneidensis, but little or no Pu(III) production was observed in cultures containing G. metallireducens. In the presence of EDTA, most of the Pu(IV)(OH)4(am) present was reduced to Pu(III) and remained soluble in cell suspensions of both S. oneidensis and G. metallireducens. When soluble Pu(IV)(EDTA) was provided as the terminal electron acceptor, cell suspensions of both S. oneidensis and G. metallireducens rapidly reduced Pu(IV)(EDTA) to Pu(III)(EDTA) with nearly complete reduction within 20 to 40 min, depending on the initial concentration. Neither bacterium was able to use Pu(IV) (in any of the forms used) as a terminal electron acceptor to support growth. These results have significant implications for the potential remediation of plutonium and suggest that strongly reducing environments where complexing ligands are present may produce soluble forms of reduced Pu species.

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