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 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.

Effect of ascorbate on oxygen uptake and growth of Escherichia coli B

1988 ◽  
Vol 34 (6) ◽  
pp. 822-824 ◽  
Author(s):  
Holly E. Richter ◽  
Jacek Switala ◽  
Peter C. Loewen
Keyword(s):  
Escherichia Coli ◽  
Oxygen Uptake ◽  
Electron Acceptor ◽  
Minimal Medium ◽  
Anaerobic Growth ◽  
Rich Medium ◽  
Terminal Electron Acceptor ◽  
Subsequent Change ◽  
Escherichia Coli B

The addition of ascorbate to aerobically growing cultures of Escherichia coli B caused only a short pause in growth and no subsequent change in the rate or extent of growth. The effect of ascorbate on oxygen uptake varied from inhibition in minimal medium to stimulation in rich medium. Cyanide-resistant growth and oxygen uptake were stimulated by ascorbate. Both the rate and extent of anaerobic growth were stimulated in proportion to the amount of ascorbate added when fumarate was the terminal electron acceptor. Ascorbate had no effect on any aspect of anaerobic growth in the absence of a terminal electron acceptor or in the presence of nitrate.

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.

scholarly journals Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Monique S. Patzner ◽  
Carsten W. Mueller ◽  
Miroslava Malusova ◽  
Moritz Baur ◽  
Verena Nikeleit ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Sink ◽  
Mineral Dissolution ◽  
Dynamic Interactions ◽  
Terminal Electron Acceptor ◽  
Iron Mineral ◽  
Permafrost Thaw ◽  
Reducing Conditions ◽  
Carbon Release ◽  
Reducing Bacteria

AbstractIt has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap organic carbon in soils overlying intact permafrost, and may limit carbon mobilization and degradation as it is observed in other environments. However, the use of iron(III)-bearing minerals as terminal electron acceptors in permafrost environments, and thus their stability and capacity to prevent carbon mobilization during permafrost thaw, is poorly understood. We have followed the dynamic interactions between iron and carbon using a space-for-time approach across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost thaw. We show through bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS) that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost (41.8 ± 10.8 mg carbon per g soil, 9.9 to 14.8% of total soil organic carbon). During permafrost thaw, water-logging and O2 limitation lead to reducing conditions and an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient. By providing a terminal electron acceptor, this rusty carbon sink is effectively destroyed along the thaw gradient and cannot prevent carbon release with thaw.

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.

The influence of potassium dichromate on dissimilatory reduction of sulfate and nitrate ions by bacteria Desulfovibrio sp.

2017 ◽  
Vol 28 (1-2) ◽  
pp. 84-95
Author(s):  
O. M. Moroz ◽  
S. O. Hnatush ◽  
Ch. I. Bohoslavets ◽  
T. M. Hrytsun’ ◽  
B. M. Borsukevych
Keyword(s):  
Electron Acceptor ◽  
Potassium Dichromate ◽  
Anaerobic Respiration ◽  
Sulfate Reducing Bacteria ◽  
Negative Influence ◽  
Electron Acceptors ◽  
Metal Compounds ◽  
Nitrate Ions ◽  
Sulfate Reducing ◽  
Reducing Bacteria

Sulfate reducing bacteria, capable to reductive transformation of different nature pollutants, used in biotechnologies of purification of sewage, contaminated by carbon, sulfur, nitrogen and metal compounds. H2S formed by them sediment metals to form of insoluble sulfides. Number of metals can be used by these microorganisms as electron acceptors during anaerobic respiration. Because under the influence of metal compounds observed slowing of bacteria metabolism, selection isolated from technologically modified ecotops resistant to pollutions strains is important task to create a new biotechnologies of purification. That’s why the purpose of this work was to study the influence of potassium dichromate, present in medium, on reduction of sulfate and nitrate ions by sulfate reducing bacteria Desulfovibrio desulfuricans IMV K-6, Desulfovibrio sp. Yav-6 and Desulfovibrio sp. Yav-8, isolated from Yavorivske Lake, to estimate the efficiency of possible usage of these bacteria in technologies of complex purification of environment from dangerous pollutants. Bacteria were cultivated in modified Kravtsov-Sorokin medium without SO42- and FeCl2×4H2O for 10 days. To study the influence of K2Cr2O7 on usage by bacteria SO42- or NO3- cells were seeded to media with Na2SO4×10H2O or NaNO3 and K2Cr2O7 at concentrations of 1.74 mM for total content of electron acceptors in medium 3.47 mM (concentration of SO42- in medium of standard composition). Cells were also seeded to media with 3.47 mM Na2SO4×10H2O, NaNO3 or K2Cr2O7 to investigate their growth in media with SO42-, NO3- or Cr2O72- as sole electron acceptor (control). Biomass was determined by turbidymetric method, content of sulfate, nitrate, dichromate, chromium (III) ions, hydrogen sulfide or ammonia ions in cultural liquid – by spectrophotometric method. It was found that K2Cr2O7 inhibits growth (2.2 and 1.3 times) and level of reduction by bacteria sulfate or nitrate ions (4.2 and 3.0 times, respectively) at simultaneous addition into cultivation medium of 1.74 mM SO42- or NO3- and 1.74 mM Cr2O72-, compared with growth and level of reduction of sulfate or nitrate ions in medium only with SO42- or NO3- as sole electron acceptor. Revealed that during cultivation of bacteria in presence of equimolar amount of SO42- or NO3- and Cr2O72-, last used by bacteria faster, content of Cr3+ during whole period of bacteria cultivation exceeded content H2S or NH4+. K2Cr2O7 in medium has most negative influence on dissimilatory reduction by bacteria SO42- than NO3-, since level of nitrate ions reduction by cells in medium with NO3- and Cr2O72- was a half times higher than level of sulfate ions reduction by it in medium with SO42- and Cr2O72-. The ability of bacteria Desulfovibrio sp. to priority reduction of Cr2O72- and after their exhaustion − NO3- and SO42- in the processes of anaerobic respiration can be used in technologies of complex purification of environment from toxic compounds.

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