Degeneration of biogenic superparamagnetic magnetite

  1. Y.-L. LI1,
  2. S. M. PFIFFNER2,
  3. M. D. DYAR3,
  4. H. VALI4,
  5. K. KONHAUSER5,
  6. D.R. COLE6,
  7. A. J. RONDINONE6,
  8. T. J. PHELPS7

Article first published online: 8 JAN 2009

DOI: 10.1111/j.1472-4669.2008.00186.x

Issue

Geobiology

Geobiology

Volume 7, Issue 1, pages 25–34, January 2009

Additional Information

How to Cite

LI, Y.-L., PFIFFNER, S. M., DYAR, M. D., VALI, H., KONHAUSER, K., COLE, D.R., RONDINONE, A. J. and PHELPS, T. J. (2009), Degeneration of biogenic superparamagnetic magnetite. Geobiology, 7: 25–34. doi: 10.1111/j.1472-4669.2008.00186.x

Author Information

  1. 1

    Department of Earth Sciences and School of Biological Sciences, The University of Hong Kong, Hong Kong

  2. 2

    Center for Environmental Biotechnology, The University of Tennessee, Knoxville, TN 37966, USA

  3. 3

    Department of Astronomy, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA

  4. 4

    Department of Earth and Planetary Sciences, 3640 University Street, McGill University, Montreal, Quebec H3A 2B2, Canada

  5. 5

    Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G2E3, Canada

  6. 6

    Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

  7. 7

    Biological Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

*Corresponding author: Y.-L. Li. Tel.: (852) 28598021; fax: (852) 25176912; e-mail: yiliang@hku.hk

Publication History

  1. Issue published online: 5 FEB 2009
  2. Article first published online: 8 JAN 2009
  3. Received 28 August 2008; accepted 10 December 2008

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ABSTRACT

Magnetite crystals precipitated as a consequence of Fe(III) reduction by Shewanella algae BrY after 265 h incubation and 5-year anaerobic storage were investigated with transmission electron microscopy, Mössbauer spectroscopy and X-ray diffraction. The magnetite crystals were typically superparamagnetic with an approximate size of 13 nm. The lattice constants of the 265 h and 5-year crystals are 8.4164Å and 8.3774Å, respectively. The Mössbauer spectra indicated that the 265 h magnetite had excess Fe(II) in its crystal-chemistry (Fe3+1.990Fe2+1.015O4) but the 5-year magnetite was Fe(II)-deficient in stoichiometry (Fe3+2.388Fe2+0.419O4). Such crystal-chemical changes may be indicative of the degeneration of superparamagnetic magnetite through the aqueous oxidization of Fe(II) anaerobically, and the concomitant oxidation of the organic phases (fatty acid methyl esters) that were present during the initial formation of the magnetite. The observation of a corona structure on the aged magnetite corroborates the anaerobic oxidation of Fe(II) on the outer layers of magnetite crystals. These results suggest that there may be a possible link between the enzymatic activity of the bacteria and the stability of Fe(II)-excess magnetite, which may help explain why stable nano-magnetite grains are seldom preserved in natural environments.

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