Coupled Fe(II)-Fe(III) electron and atom exchange as a mechanism for Fe isotope fractionation during dissimilatory iron oxide reduction.

Microbial dissimilatory iron reduction (DIR) is an important pathway for carbon oxidation in anoxic sediments, and iron isotopes may distinguish between iron produced by DIR and other sources of aqueous Fe(II). Previous studies have shown that aqueous Fe(II) produced during the earliest stages of DIR has delta56Fe values that are 0.5-2.0%o lowerthan the initial Fe(III) substrate. The new experiments reported here suggest that this fractionation is controlled by coupled electron and Fe atom exchange between Fe(II) and Fe(III) at iron oxide surfaces. In hematite and goethite reduction experiments with Geobacter sulfurreducens, the 56Fe/54Fe isotopic fractionation between aqueous Fe(II) and the outermost layers of Fe(III) on the oxide surface is approximately -3%o and can be explained by equilibrium Fe isotope partitioning between reactive Fe(II) and Fe(III) pools that coexist during DIR. The results indicate that sorption of Fe(II) to Fe(III) substrates cannot account for production of low-delta56Fe values for aqueous Fe(II) during DIR.

[1]  E. Roden.  Geochemical and microbiological controls on dissimilatory iron reduction. Comptes Rendus , 2006 .

[2]  J. McManus,et al.  The effect of early diagenesis on the Fe isotope compositions of porewaters and authigenic minerals in continental margin sediments , 2006 .

[3]  H. Ohmoto,et al.  Biogeochemical cycling of iron in the Archean–Paleoproterozoic Earth: Constraints from iron isotope variations in sedimentary rocks from the Kaapvaal and Pilbara Cratons , 2005 .

[4]  E. Roden,et al.  Experimental constraints on Fe isotope fractionation during magnetite and Fe carbonate formation coupled to dissimilatory hydrous ferric oxide reduction , 2005 .

[5]  Byong-Hun Jeon,et al.  Low-Temperature Oxygen Trap for Maintaining Strict Anoxic Conditions , 2004 .

[6]  E. Roden,et al.  Microbial reduction of U(VI) at the solid-water interface. , 2004, Environmental science & technology.

[7]  M. Scherer,et al.  Spectroscopic evidence for Fe(II)-Fe(III) electron transfer at the iron oxide-water interface. , 2004, Environmental science & technology.

[8]  A. Anbar,et al.  Fe isotopic fractionation during mineral dissolution with and without bacteria , 2004 .

[9]  P. Nico,et al.  Structural constraints of ferric (hydr)oxides on dissimilatory iron reduction and the fate of Fe(II) , 2004 .

[10]  A. Anbar,et al.  Iron isotope fractionation during microbial reduction of iron: The importance of adsorption , 2004 .

[11]  J A Eisen,et al.  Genome of Geobacter sulfurreducens: Metal Reduction in Subsurface Environments , 2003, Science.

[12]  Donald R. Metzler,et al.  Stimulating the In Situ Activity of Geobacter Species To Remove Uranium from the Groundwater of a Uranium-Contaminated Aquifer , 2003, Applied and Environmental Microbiology.

[13]  R. Kukkadapu,et al.  Secondary Mineralization Pathways Induced by Dissimilatory Iron Reduction of Ferrihydrite Under Advective Flow , 2003 .

[14]  Byong-Hun Jeon,et al.  Kinetics and mechanisms for reactions of Fe(II) with iron(III) oxides. , 2003, Environmental science & technology.

[15]  Henry J Sun,et al.  Application of Fe isotopes to tracing the geochemical and biological cycling of Fe , 2003 .

[16]  Steven C. Smith,et al.  Nonlocal bacterial electron transfer to hematite surfaces , 2003 .

[17]  N. Beukes,et al.  Ancient geochemical cycling in the Earth as inferred from Fe isotope studies of banded iron formations from the Transvaal Craton , 2003 .

[18]  S. Welch,et al.  Kinetic and equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III) , 2002 .

[19]  Kelly P. Nevin,et al.  Mechanisms for Accessing Insoluble Fe(III) Oxide during Dissimilatory Fe(III) Reduction by Geothrix fermentans , 2002, Applied and Environmental Microbiology.

[20]  R. Schwarzenbach,et al.  Reduction of polyhalogenated methanes by surface-bound Fe(II) in aqueous suspensions of iron oxides. , 2002, Environmental science & technology.

[21]  Kelly P. Nevin,et al.  Mechanisms for Fe(III) Oxide Reduction in Sedimentary Environments , 2002 .

[22]  Eric E. Roden,et al.  Influence of Biogenic Fe(II) on Bacterial Crystalline Fe(III) Oxide Reduction , 2002 .

[23]  Steven C. Smith,et al.  Biomineralization of Poorly Crystalline Fe(III) Oxides by Dissimilatory Metal Reducing Bacteria (DMRB) , 2002 .

[24]  Henry J Sun,et al.  Isotopic fractionation between Fe(III) and Fe(II) in aqueous solutions , 2002 .

[25]  Byong-Hun Jeon,et al.  Reactions of ferrous iron with hematite , 2001 .

[26]  W. Röling,et al.  Relationships between Microbial Community Structure and Hydrochemistry in a Landfill Leachate-Polluted Aquifer , 2001, Applied and Environmental Microbiology.

[27]  Steven C. Smith,et al.  Dissimilatory bacterial reduction of Al-substituted goethite in subsurface sediments , 2001 .

[28]  C. W. Childs,et al.  Demonstration of significant abiotic iron isotope fractionation in nature , 2001 .

[29]  S. Brantley,et al.  Fractionation of Fe isotopes by soil microbes and organic acids , 2001 .

[30]  J. Zachara,et al.  Microbial reduction of Fe(III) and sorption/precipitation of Fe(II) on Shewanella putrefaciens strain CN32. , 2001, Environmental science & technology.

[31]  K. Nealson,et al.  Bacterial and archaeal populations associated with freshwater ferromanganous micronodules and sediments. , 2001, Environmental microbiology.

[32]  Dianne K. Newman,et al.  A role for excreted quinones in extracellular electron transfer , 2000, Nature.

[33]  Derek R. Lovley,et al.  Lack of Production of Electron-Shuttling Compounds or Solubilization of Fe(III) during Reduction of Insoluble Fe(III) Oxide by Geobacter metallireducens , 2000, Applied and Environmental Microbiology.

[34]  Laurent Charlet,et al.  Surface catalysis of uranium(VI) reduction by iron(II) , 1999 .

[35]  K. Nealson,et al.  Iron isotope biosignatures. , 1999, Science.

[36]  E. Roden,et al.  Ferrous iron removal promotes microbial reduction of crystalline iron(III) oxides , 1999 .

[37]  Steven C. Smith,et al.  Bacterial reduction of crystalline Fe3+ oxides in single phase suspensions and subsurface materials , 1998 .

[38]  T. Onstott,et al.  BIOGENIC IRON MINERALIZATION ACCOMPANYING THE DISSIMILATORY REDUCTION OF HYDROUS FERRIC OXIDE BY A GROUNDWATER BACTERIUM , 1998 .

[39]  Derek R. Lovley,et al.  Microbiological evidence for Fe(III) reduction on early Earth , 1998, Nature.

[40]  John M. Zachara,et al.  Microbial Reduction of Crystalline Iron(III) Oxides: Influence of Oxide Surface Area and Potential for Cell Growth , 1996 .

[41]  E. Roden,et al.  Dissimilatory Fe(III) Reduction by the Marine Microorganism Desulfuromonas acetoxidans , 1993, Applied and environmental microbiology.

[42]  R. Blakemore,et al.  A Hydrogen-Oxidizing, Fe(III)-Reducing Microorganism from the Great Bay Estuary, New Hampshire , 1992, Applied and environmental microbiology.

[43]  J. Bowles.  Iron Oxides in the Laboratory , 1992, Mineralogical Magazine.

[44]  Kelly P. Nevin,et al.  Dissimilatory Fe(III) and Mn(IV) reduction. , 1991, Advances in microbial physiology.

[45]  D. Lovley,et al.  Novel Mode of Microbial Energy Metabolism: Organic Carbon Oxidation Coupled to Dissimilatory Reduction of Iron or Manganese , 1988, Applied and environmental microbiology.

[46]  Derek R. Lovley,et al.  Anaerobic production of magnetite by a dissimilatory iron-reducing microorganism , 1987, Nature.

[47]  D. Sherman.  Molecular orbital (SCF-Xα-SW) theory of metal-metal charge transfer processes in minerals , 1987 .

[48]  D. Lovley,et al.  Availability of Ferric Iron for Microbial Reduction in Bottom Sediments of the Freshwater Tidal Potomac River , 1986, Applied and environmental microbiology.

[49]  L. Stookey.  Ferrozine---a new spectrophotometric reagent for iron , 1970 .

[50]  E. Roden,et al.  Anaerobic redox cycling of iron by freshwater sediment microorganisms. , 2006, Environmental microbiology.

[51]  K. Nealson,et al.  Isotopic Constraints on Biogeochemical Cycling of Fe , 2004 .

[52]  Byong-Hun Jeon,et al.  Inhibition of biological reductive dissolution of hematite by ferrous iron. , 2004, Environmental science & technology.

[53]  E. Schauble.  Applying Stable Isotope Fractionation Theory to New Systems , 2004 .

[54]  D. Canfield.  Biogeochemistry of Sulfur Isotopes , 2001 .

[55]  Steven C. Smith,et al.  Solubilization of Fe(III) oxide-bound trace metals by a dissimilatory Fe(III) reducing bacterium , 2001 .

[56]  D. Lovley.  Fe(III) and Mn(IV) Reduction , 2000 .

[57]  K. Ludwig.  ISOPLOT; a plotting and regression program for radiogenic-isotope data; version 2.53 , 1991 .