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California Polytechnic State University, San Luis Obispo

Magnetotactic bacteria

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Crystal-Size Distributions And Possible Biogenic Origin Of Fe Sulfides, Mihály Pósfai, Krisztina Cziner, Emö Márton, Péter Márton, Peter R. Buseck, Richard B. Frankel, Dennis A. Bazylinski Jul 2001

Crystal-Size Distributions And Possible Biogenic Origin Of Fe Sulfides, Mihály Pósfai, Krisztina Cziner, Emö Márton, Péter Márton, Peter R. Buseck, Richard B. Frankel, Dennis A. Bazylinski

Physics

Sedimentary greigite (Fe3S4) can form either by ''biologically controlled'' or by ''biologically induced mineralization'' (BCM and BIM, respectively). In order to identify the origin of magnetic Fe sulfides, we studied and compared the sizes and morphologies of greigite crystals produced by a magnetotactic microorganism (previously described and referred to as the ''many-celled magnetotactic prokaryote'', MMP) and Fe sulfides from two specimens of Miocene sedimentary rocks (from Łaka, in the foredeep of the Western Carpathians and from Michalovce, in the Transcarpathian Depression). Greigite grains from the MMP and the Łaka rock show nearly Gaussian crystal-size distributions (CSDs), whereas ...


Off-Axis Electron Holography Of Magnetotactic Bacteria: Magnetic Microstructure Of Strains Mv-1 And Ms-1, R. E. Dunin-Borkowski, Martha R. Mccartney, Mihály Pósfai, Richard B. Frankel, Dennis A. Bazylinski, Peter R. Buseck Jul 2001

Off-Axis Electron Holography Of Magnetotactic Bacteria: Magnetic Microstructure Of Strains Mv-1 And Ms-1, R. E. Dunin-Borkowski, Martha R. Mccartney, Mihály Pósfai, Richard B. Frankel, Dennis A. Bazylinski, Peter R. Buseck

Physics

Off-axis electron holography in the transmission electron microscope is used to characterize the magnetic microstructure of magnetotactic bacteria. The practical details of the technique are illustrated through the examination of single cells of strains MV-1 and MS-1, which contain crystals of magnetite (Fe3O4) that are ~50nm in size and are arranged in chains. Electron holography allows the magnetic domain structures within the nanocrystals to be visualized directly at close to the nanometer scale. The crystals are shown to be single magnetic domains. The magnetization directions of small crystals that would be superparamagnetic if they were isolated are ...