Organic matter mineralization with reduction of ferric iron in anaerobic sediments.
01 Apr 1986-Applied and Environmental Microbiology (American Society for Microbiology)-Vol. 51, Iss: 4, pp 683-689
TL;DR: Results indicate that iron reduction can outcompete methanogenic food chains for sediment organic matter when amorphous ferric oxyhydroxides are available in anaerobic sediments, and the transfer of electrons from organic matter to ferric iron can be a major pathway for organic matter decomposition.
Abstract: The potential for ferric iron reduction with fermentable substrates, fermentation products, and complex organic matter as electron donors was investigated with sediments from freshwater and brackish water sites in the Potomac River Estuary. In enrichments with glucose and hematite, iron reduction was a minor pathway for electron flow, and fermentation products accumulated. The substitution of amorphous ferric oxyhydroxide for hematite in glucose enrichments increased iron reduction 50-fold because the fermentation products could also be metabolized with concomitant iron reduction. Acetate, hydrogen, propionate, butyrate, ethanol, methanol, and trimethylamine stimulated the reduction of amorphous ferric oxyhydroxide in enrichments inoculated with sediments but not in uninoculated or heat-killed controls. The addition of ferric iron inhibited methane production in sediments. The degree of inhibition of methane production by various forms of ferric iron was related to the effectiveness of these ferric compounds as electron acceptors for the metabolism of acetate. The addition of acetate or hydrogen relieved the inhibition of methane production by ferric iron. The decrease of electron equivalents proceeding to methane in sediments supplemented with amorphous ferric oxyhydroxides was compensated for by a corresponding increase of electron equivalents in ferrous iron. These results indicate that iron reduction can outcompete methanogenic food chains for sediment organic matter. Thus, when amorphous ferric oxyhydroxides are available in anaerobic sediments, the transfer of electrons from organic matter to ferric iron can be a major pathway for organic matter decomposition.
Citations
More filters
TL;DR: The physiological characteristics of Geobacter species appear to explain why they have consistently been found to be the predominant Fe(III)- and Mn(IV)-reducing microorganisms in a variety of sedimentary environments.
2,633 citations
TL;DR: This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe( III), Mn( IV), or Mn (IV) reduction can yield energy for microbial growth.
Abstract: A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe(3)O(4)). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35 degrees C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO(2) was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO(3)). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments.
2,233 citations
TL;DR: The results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.
Abstract: Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 micro M), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 micro mol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (E(o)' =+0.37 V). The production of current in microbial fuel cell (65 mA/m(2) of electrode surface) or poised-potential (163 to 1,143 mA/m(2)) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.
2,133 citations
Cites background from "Organic matter mineralization with ..."
...poorly crystalline Fe(III) oxide (17) as the electron acceptor....
[...]
TL;DR: In this article, it was shown that some microorganisms found in soils and sediments are able to use humic substances as an electron acceptor for the anaerobic oxidation of organic compounds and hydrogen.
Abstract: HUMIC substances are heterogeneous high-molecular-weight organic materials which are ubiquitous in terrestrial and aquatic environments. They are resistant to microbial degradation1 and thus are not generally considered to be dynamically involved in microbial metabolism, especially in anoxic habitats. However, we show here that some microorganisms found in soils and sediments are able to use humic substances as an electron acceptor for the anaerobic oxidation of organic compounds and hydrogen. This electron transport yields energy to support growth. Microbial humic reduction also enhances the capacity for microorganisms to reduce other, less accessible electron acceptors, such as insoluble Fe(III) oxides, because humic substances can shuttle electrons between the humic-reducing microorganisms and the Fe(III) oxide. The finding that microorganisms can donate electrons to humic acids has important implications for the mechanisms by which microorganisms oxidize both natural and contaminant organics in anaerobic soils and sediments, and suggests a biological source of electrons for humics-mediated reduction of contaminant metals and organics.
1,651 citations
TL;DR: A novel microorganism is reported on, Rhodoferax ferrireducens, that can oxidize glucose to CO2 and quantitatively transfer electrons to graphite electrodes without the need for an electron-shuttling mediator, which results in stable, long-term power production.
Abstract: Abundant energy, stored primarily in the form of carbohydrates, can be found in waste biomass from agricultural, municipal and industrial sources as well as in dedicated energy crops, such as corn and other grains. Potential strategies for deriving useful forms of energy from carbohydrates include production of ethanol and conversion to hydrogen, but these approaches face technical and economic hurdles. An alternative strategy is direct conversion of sugars to electrical power. Existing transition metal-catalyzed fuel cells cannot be used to generate electric power from carbohydrates. Alternatively, biofuel cells in which whole cells or isolated redox enzymes catalyze the oxidation of the sugar have been developed, but their applicability has been limited by several factors, including (i) the need to add electron-shuttling compounds that mediate electron transfer from the cell to the anode, (ii) incomplete oxidation of the sugars and (iii) lack of long-term stability of the fuel cells. Here we report on a novel microorganism, Rhodoferax ferrireducens, that can oxidize glucose to CO(2) and quantitatively transfer electrons to graphite electrodes without the need for an electron-shuttling mediator. Growth is supported by energy derived from the electron transfer process itself and results in stable, long-term power production.
1,454 citations
References
More filters
TL;DR: Pore water profiles of total CO 2, pH, PO 3−4, NO − 3 plus NO − 2, SO 2− 4, S 2−, Fe 2+ and Mn 2+ have been obtained in cores from pelagic sediments of the eastern equatorial Atlantic under waters of moderate to high productivity as mentioned in this paper.
3,045 citations
"Organic matter mineralization with ..." refers background in this paper
...The accumulation of Fe(II) in sediments prior to sulfate reduction or methane production (4, 8) suggests that Fe(III)reducing bacteria, or food chains of Fe(III)-reducing bacte-...
[...]
...The accumulation of Fe(II) before the reduction of sulfate in pore water depth profiles and incubated sediments suggests that Fe(III) can also outcompete sulfate reduction for electon donors (4, 8, 15)....
[...]
...of organic matter with Fe(III) as the electron acceptor is theoretically possible and is more thermodynamically favorable than the mineralization of organic matter with sulfate reduction or methane production as the terminal step (4)....
[...]
TL;DR: The process of Fe reduction was most likely associated with the activity of facultative anaerobic, NO(3)-reducing bacteria, and the process may be important for mineralization in situ if the availability ofNO(3) is low.
Abstract: Studies were carried out to elucidate the nature and importance of Fe3+ reduction in anaerobic slurries of marine surface sediment. A constant accumulation of Fe2+ took place immediately after the endogenous NO3− was depleted. Pasteurized controls showed no activity of Fe3+ reduction. Additions of 0.2 mM NO3− and NO2− to the active slurries arrested the Fe3+ reduction, and the process was resumed only after a depletion of the added compounds. Extended, initial aeration of the sediment did not affect the capacity for reduction of NO3− and Fe3+, but the treatments with NO3− increased the capacity for Fe3+ reduction. Addition of 20 mM MoO42− completely inhibited the SO42− reduction, but did not affect the reduction of Fe3+. The process of Fe3+ reduction was most likely associated with the activity of facultative anaerobic, NO3−-reducing bacteria. In surface sediment, the bulk of the Fe3+ reduction may be microbial, and the process may be important for mineralization in situ if the availability of NO3− is low.
341 citations
TL;DR: In this paper, the authors report downcore magnetic profiles from undisturbed Kasten cores taken in rapidly deposited laminated sediments from the Gulf of California and in bioturbated haemipelagic muds on the Oregon continental slope which give apparently reliable directions, but show dramatic decreases in the intensities of natural (NRM) and artificial (ARM, IRM) remanences with depth.
Abstract: Rapidly deposited sediments from marine and lake environments are being used increasingly to study decadal to millennial fluctuations in the Earth's magnetic field. The objectives are to gain more fundamental understanding of the geodynamo and to establish a new dating technique for sediments. While lacustrine sections are generally restricted to temperate latitude glacial lakes (≤ 20,000 yr old), rapidly deposited marine sediments along continental margins potentially offer continuous high resolution, yet long-term records of geomagnetic secular variation. However, to interpret the sedimentary magnetic record accurately, geochemical processes that affect the reliability of the magnetic signal must be understood. We now report downcore magnetic profiles from undisturbed Kasten cores taken in rapidly deposited laminated sediments from the Gulf of California and in bioturbated haemipelagic muds on the Oregon continental slope which give apparently reliable directions, but show dramatic decreases in the intensities of natural (NRM) and artificial (ARM, IRM) remanences with depth. Downcore porewater and solid sulphur analyses show concave-down decreases in porewater sulphate and systematic increases in pyrite and metastable monosulphides. The maximum curvature of the sulphide profile occurs directly below the high magnetization zone. Combined with other compositional and mineralogical analyses, these data suggest that due to oxidative decomposition of organic matter, magnetites and other iron oxides become progressively reduced and subsequently sulphidized and pyritized with depth. Iron reduction seems to occur before sulphide formation. Changes in magnetic stability parameters are consistent with selective dissolution of the finer-sized grains causing downcore coarsening of the magnetic fraction.
330 citations
"Organic matter mineralization with ..." refers background in this paper
...The accumulation of Fe(II) before the reduction of sulfate in pore water depth profiles and incubated sediments suggests that Fe(III) can also outcompete sulfate reduction for electon donors (4, 8, 15)....
[...]
...The accumulation of Fe(II) in sediments prior to sulfate reduction or methane production (4, 8) suggests that Fe(III)reducing bacteria, or food chains of Fe(III)-reducing bacteria, can outcompete sulfate-reducing and methane-producing food chains for organic matter when Fe(III) is available....
[...]
TL;DR: In this article, a model based on the in situ physiological characteristics of methanogens and sulfate reducers was developed to predict the relative importance of sulfate production and reduction in lakes of various trophic status.
298 citations
TL;DR: In this article, the authors compared the results obtained from oxic lake sediments and the in situ measurement of trace metal concentrations in the associated pore waters in the area of Sudbury, Ontario, to those obtained for the adsorption of the trace metals onto amorphous iron oxyhydroxides in a NaNO3 medium.
281 citations