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

2009 ◽  
Vol 75 (11) ◽  
pp. 3641-3647 ◽  
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.

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

2007 ◽  
Vol 73 (18) ◽  
pp. 5897-5903 ◽  
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.

scholarly journals Melanin Production and Use as a Soluble Electron Shuttle for Fe(III) Oxide Reduction and as a Terminal Electron Acceptor by Shewanella algae BrY

2002 ◽  
Vol 68 (5) ◽  
pp. 2436-2444 ◽  
Author(s):  
Charles E. Turick ◽  
Louis S. Tisa ◽  
Frank Caccavo,
Keyword(s):  
Electron Acceptor ◽  
Minimal Medium ◽  
Hydrous Ferric Oxide ◽  
Electron Shuttle ◽  
Melanin Production ◽  
Terminal Electron Acceptor ◽  
Iron Mineral ◽  
Shewanella Algae ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

ABSTRACT Dissimilatory metal-reducing bacteria (DMRB) utilize numerous compounds as terminal electron acceptors, including insoluble iron oxides. The mechanism(s) of insoluble-mineral reduction by DMRB is not well understood. Here we report that extracellular melanin is produced by Shewanella algae BrY. The extracted melanin served as the sole terminal electron acceptor. Upon reduction the reduced, soluble melanin reduced insoluble hydrous ferric oxide in the absence of bacteria, thus demonstrating that melanin produced by S. algae BrY is a soluble Fe(III)-reducing compound. In the presence of bacteria, melanin acted as an electron conduit to Fe(III) minerals and increased Fe(III) mineral reduction rates. Growth of S. algae BrY occurred in anaerobic minimal medium supplemented with melanin extracted from previously grown aerobic cultures of S. algae BrY. Melanin produced by S. algae BrY imparts increased versatility to this organism as a soluble Fe(III) reductant, an electron conduit for iron mineral reduction, and a sole terminal electron acceptor that supports growth.

scholarly journals Complex Iron Uptake by the Putrebactin-Mediated and Feo Systems in Shewanella oneidensis

2018 ◽  
Vol 84 (20) ◽  
Author(s):  
Lulu Liu ◽  
Shisheng Li ◽  
Sijing Wang ◽  
Ziyang Dong ◽  
Haichun Gao
Keyword(s):  
Iron Uptake ◽  
Iron Homeostasis ◽  
Shewanella Oneidensis ◽  
Special Role ◽  
Uptake System ◽  
Biological Processes ◽  
Content Type ◽  
Iron Uptake System ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

ABSTRACT Shewanella oneidensis is an extensively studied bacterium capable of respiring minerals, including a variety of iron ores, as terminal electron acceptors (EAs). Although iron plays an essential and special role in iron respiration of S. oneidensis, little has been done to date to investigate the characteristics of iron transport in this bacterium. In this study, we found that all proteins encoded by the pub-putA-putB cluster for putrebactin (S. oneidensis native siderophore) synthesis (PubABC), recognition-transport of Fe3+-putrebactin across the outer membrane (PutA), and reduction of ferric putrebactin (PutB) are essential to putrebactin-mediated iron uptake. Although homologs of PutA are many, none can function as its replacement, but some are able to work with other bacterial siderophores. We then showed that Fe2+-specific Feo is the other primary iron uptake system, based on the synthetical lethal phenotype resulting from the loss of both iron uptake routes. The role of the Feo system in iron uptake appears to be more critical, as growth is significantly impaired by the absence of the system but not of putrebactin. Furthermore, we demonstrate that hydroxyl acids, especially α-types such as lactate, promote iron uptake in a Feo-dependent manner. Overall, our findings underscore the importance of the ferrous iron uptake system in metal-reducing bacteria, providing an insight into iron homeostasis by linking these two biological processes. IMPORTANCE S. oneidensis is among the first- and the best-studied metal-reducing bacteria, with great potential in bioremediation and biotechnology. However, many questions regarding mechanisms closely associated with those applications, such as iron homeostasis, including iron uptake, export, and regulation, remain to be addressed. Here we show that Feo is a primary player in iron uptake in addition to the siderophore-dependent route. The investigation also resolved a few puzzles regarding the unexpected phenotypes of the putA mutant and lactate-dependent iron uptake. By elucidating the physiological roles of these two important iron uptake systems, this work revealed the breadth of the impacts of iron uptake systems on the biological processes.

scholarly journals Genetic Characterization of a Single Bifunctional Enzyme for Fumarate Reduction and Succinate Oxidation in Geobacter sulfurreducens and Engineering of Fumarate Reduction in Geobacter metallireducens

2006 ◽  
Vol 188 (2) ◽  
pp. 450-455 ◽  
Author(s):  
Jessica E. Butler ◽  
Richard H. Glaven ◽  
Abraham Esteve-Núñez ◽  
Cinthia Núñez ◽  
Evgenya S. Shelobolina ◽  
...  
Keyword(s):  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Mutant Strain ◽  
Electron Acceptor ◽  
Geobacter Sulfurreducens ◽  
Fumarate Reductase ◽  
Succinate Dehydrogenase Activity ◽  
Geobacter Metallireducens ◽  
Terminal Electron Acceptor ◽  
Fumarate Reduction

ABSTRACT The mechanism of fumarate reduction in Geobacter sulfurreducens was investigated. The genome contained genes encoding a heterotrimeric fumarate reductase, FrdCAB, with homology to the fumarate reductase of Wolinella succinogenes and the succinate dehydrogenase of Bacillus subtilis. Mutation of the putative catalytic subunit of the enzyme resulted in a strain that lacked fumarate reductase activity and was unable to grow with fumarate as the terminal electron acceptor. The mutant strain also lacked succinate dehydrogenase activity and did not grow with acetate as the electron donor and Fe(III) as the electron acceptor. The mutant strain could grow with acetate as the electron donor and Fe(III) as the electron acceptor if fumarate was provided to alleviate the need for succinate dehydrogenase activity in the tricarboxylic acid cycle. The growth rate of the mutant strain under these conditions was faster and the cell yields were higher than for wild type grown under conditions requiring succinate dehydrogenase activity, suggesting that the succinate dehydrogenase reaction consumes energy. An orthologous frdCAB operon was present in Geobacter metallireducens, which cannot grow with fumarate as the terminal electron acceptor. When a putative dicarboxylic acid transporter from G. sulfurreducens was expressed in G. metallireducens, growth with fumarate as the sole electron acceptor was possible. These results demonstrate that, unlike previously described organisms, G. sulfurreducens and possibly G. metallireducens use the same enzyme for both fumarate reduction and succinate oxidation in vivo.

scholarly journals Effect of the Deletion of qmoABC and the Promoter-Distal Gene Encoding a Hypothetical Protein on Sulfate Reduction in Desulfovibrio vulgaris Hildenborough

2010 ◽  
Vol 76 (16) ◽  
pp. 5500-5509 ◽  
Author(s):  
Grant M. Zane ◽  
Huei-che Bill Yen ◽  
Judy D. Wall
Keyword(s):  
Sulfate Reduction ◽  
Electron Acceptor ◽  
Transmembrane Protein ◽  
Hypothetical Protein ◽  
Desulfovibrio Vulgaris ◽  
Gene Encoding ◽  
Terminal Electron Acceptor ◽  
Sulfate Reducing ◽  
Reducing Bacteria

ABSTRACTThe pathway of electrons required for the reduction of sulfate in sulfate-reducing bacteria (SRB) is not yet fully characterized. In order to determine the role of a transmembrane protein complex suggested to be involved in this process, a deletion inDesulfovibrio vulgarisHildenborough was created by marker exchange mutagenesis that eliminated four genes putatively encoding the QmoABC complex and a hypothetical protein (DVU0851). The Qmo (quinone-interactingmembrane-boundoxidoreductase) complex is proposed to be responsible for transporting electrons to the dissimilatory adenosine-5′-phosphosulfate reductase in SRB. In support of the predicted role of this complex, the deletion mutant was unable to grow using sulfate as its sole electron acceptor with a range of electron donors. To explore a possible role for the hypothetical protein in sulfate reduction, a second mutant was constructed that had lost only the gene that codes for the DVU0851 protein. The second constructed mutant grew with sulfate as the sole electron acceptor; however, there was a lag that was not present with the wild-type or complemented strain. Neither deletion strain was significantly impaired for growth with sulfite or thiosulfate as the terminal electron acceptor. Complementation of the Δ(qmoABC-DVU0851) mutant with all four genes or only theqmoABCgenes restored its ability to grow by sulfate respiration. These results confirmed the prediction that the Qmo complex is in the electron pathway for sulfate reduction and revealed that no other transmembrane complex could compensate when Qmo was lacking.

Steady state protein levels in Geobacter metallireducens grown with iron (III) citrate or nitrate as terminal electron acceptor

PROTEOMICS ◽  
2007 ◽  
Vol 7 (22) ◽  
pp. 4148-4157 ◽  
Author(s):  
Angela J. Ahrendt ◽  
Sandra L. Tollaksen ◽  
Carl Lindberg ◽  
Wenhong Zhu ◽  
John R. Yates ◽  
...  
Keyword(s):  
Steady State ◽  
Electron Acceptor ◽  
Geobacter Metallireducens ◽  
Terminal Electron Acceptor ◽  
Protein Levels

scholarly journals Patterns in Wetland Microbial Community Composition and Functional Gene Repertoire Associated with Methane Emissions

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Shaomei He ◽  
Stephanie A. Malfatti ◽  
Jack W. McFarland ◽  
Frank E. Anderson ◽  
Amrita Pati ◽  
...  
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Greenhouse Gas ◽  
Community Composition ◽  
Electron Acceptor ◽  
Methane Production ◽  
Microbial Community Composition ◽  
Restored Wetland ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

ABSTRACTWetland restoration on peat islands previously drained for agriculture has potential to reverse land subsidence and sequester atmospheric carbon dioxide as peat accretes. However, the emission of methane could potentially offset the greenhouse gas benefits of captured carbon. As microbial communities play a key role in governing wetland greenhouse gas fluxes, we are interested in how microbial community composition and functions are associated with wetland hydrology, biogeochemistry, and methane emission, which is critical to modeling the microbial component in wetland methane fluxes and to managing restoration projects for maximal carbon sequestration. Here, we couple sequence-based methods with biogeochemical and greenhouse gas measurements to interrogate microbial communities from a pilot-scale restored wetland in the Sacramento-San Joaquin Delta of California, revealing considerable spatial heterogeneity even within this relatively small site. A number of microbial populations and functions showed strong correlations with electron acceptor availability and methane production; some also showed a preference for association with plant roots. Marker gene phylogenies revealed a diversity of major methane-producing and -consuming populations and suggested novel diversity within methanotrophs. Methanogenic archaea were observed in all samples, as were nitrate-, sulfate-, and metal-reducing bacteria, indicating that no single terminal electron acceptor was preferred despite differences in energetic favorability and suggesting spatial microheterogeneity and microniches. Notably, methanogens were negatively correlated with nitrate-, sulfate-, and metal-reducing bacteria and were most abundant at sampling sites with high peat accretion and low electron acceptor availability, where methane production was highest.IMPORTANCEWetlands are the largest nonanthropogenic source of atmospheric methane but also a key global carbon reservoir. Characterizing belowground microbial communities that mediate carbon cycling in wetlands is critical to accurately predicting their responses to changes in land management and climate. Here, we studied a restored wetland and revealed substantial spatial heterogeneity in biogeochemistry, methane production, and microbial communities, largely associated with the wetland hydraulic design. We observed patterns in microbial community composition and functions correlated with biogeochemistry and methane production, including diverse microorganisms involved in methane production and consumption. We found that methanogenesis gene abundance is inversely correlated with genes from pathways exploiting other electron acceptors, yet the ubiquitous presence of genes from all these pathways suggests that diverse electron acceptors contribute to the energetic balance of the ecosystem. These investigations represent an important step toward effective management of wetlands to reduce methane flux to the atmosphere and enhance belowground carbon storage.

Treatment of sulfate-rich and low pH wastewater by sulfate reducing bacteria with iron shavings in a laboratory

2013 ◽  
Vol 69 (3) ◽  
pp. 595-600 ◽  
Author(s):  
Xiaoye Liu ◽  
Wenqi Gong ◽  
Lin Liu
Keyword(s):  
Wastewater Treatment ◽  
Organic Compounds ◽  
Electron Acceptor ◽  
Sulfate Reducing Bacteria ◽  
Low Ph ◽  
Synthetic Wastewater ◽  
Acidic Environment ◽  
Terminal Electron Acceptor ◽  
Sulfate Reducing ◽  
Reducing Bacteria

Sulfate-rich wastewater is an indirect threat to the environment especially at low pH. Sulfate reducing bacteria (SRB) could use sulfate as the terminal electron acceptor for the degradation of organic compounds and hydrogen transferring SO42− to H2S. However their acute sensitivity to acidity leads to a greatest limitation of SRB applied in such wastewater treatment. With the addition of iron shavings SRB could adapt to such an acidic environment, and 57.97, 55.05 and 14.35% of SO42− was reduced at pH 5, pH 4 and pH 3, respectively. Nevertheless it would be inhibited in too acidic an environment. The behavior of SRB after inoculation in acidic synthetic wastewater with and without iron shavings is presented, and some glutinous substances were generated in the experiments at pH 4 with SRB culture and iron shavings.

scholarly journals Hydrogen Metabolism in Shewanella oneidensis MR-1

2006 ◽  
Vol 73 (4) ◽  
pp. 1153-1165 ◽  
Author(s):  
Galit Meshulam-Simon ◽  
Sebastian Behrens ◽  
Alexander D. Choo ◽  
Alfred M. Spormann
Keyword(s):  
Stationary Phase ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Shewanella Oneidensis ◽  
Hydrogenase Activity ◽  
Hydrogen Metabolism ◽  
Experimental Conditions ◽  
Formate Hydrogen Lyase ◽  
Fermenting Bacteria ◽  
Reverse Electron Transport

ABSTRACT Shewanella oneidensis MR-1 is a facultative sediment microorganism which uses diverse compounds, such as oxygen and fumarate, as well as insoluble Fe(III) and Mn(IV) as electron acceptors. The electron donor spectrum is more limited and includes metabolic end products of primary fermenting bacteria, such as lactate, formate, and hydrogen. While the utilization of hydrogen as an electron donor has been described previously, we report here the formation of hydrogen from pyruvate under anaerobic, stationary-phase conditions in the absence of an external electron acceptor. Genes for the two S. oneidensis MR-1 hydrogenases, hydA, encoding a periplasmic [Fe-Fe] hydrogenase, and hyaB, encoding a periplasmic [Ni-Fe] hydrogenase, were found to be expressed only under anaerobic conditions during early exponential growth and into stationary-phase growth. Analyses of ΔhydA, ΔhyaB, andΔ hydA ΔhyaB in-frame-deletion mutants indicated that HydA functions primarily as a hydrogen-forming hydrogenase while HyaB has a bifunctional role and represents the dominant hydrogenase activity under the experimental conditions tested. Based on results from physiological and genetic experiments, we propose that hydrogen is formed from pyruvate by multiple parallel pathways, one pathway involving formate as an intermediate, pyruvate-formate lyase, and formate-hydrogen lyase, comprised of HydA hydrogenase and formate dehydrogenase, and a formate-independent pathway involving pyruvate dehydrogenase. A reverse electron transport chain is potentially involved in a formate-hydrogen lyase-independent pathway. While pyruvate does not support a fermentative mode of growth in this microorganism, pyruvate, in the absence of an electron acceptor, increased cell viability in anaerobic, stationary-phase cultures, suggesting a role in the survival of S. oneidensis MR-1 under stationary-phase conditions.

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

2009 ◽  
Vol 75 (9) ◽  
pp. 2931-2935 ◽  
Author(s):  
Brian H. Lower ◽  
Ruchirej Yongsunthon ◽  
Liang Shi ◽  
Linda Wildling ◽  
Hermann J. Gruber ◽  
...  
Keyword(s):  
Cell Surface ◽  
Uniform Distribution ◽  
Electron Acceptor ◽  
Extracellular Polymeric Substance ◽  
Solid Phase ◽  
Shewanella Oneidensis ◽  
Exterior Surface ◽  
Terminal Electron Acceptor ◽  
Force Microscopy ◽  
Antibody Recognition

ABSTRACT Antibody recognition force microscopy showed that OmcA and MtrC are expressed on the exterior surface of living Shewanella oneidensis MR-1 cells when Fe(III), including solid-phase hematite (Fe2O3), was the terminal electron acceptor. OmcA was localized to the interface between the cell and mineral. MtrC displayed a more uniform distribution across the cell surface. Both cytochromes were associated with an extracellular polymeric substance.

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