Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (32) Citing Articles via Google Scholar Google Scholar Articles by DUNIN-BORKOWSKI, R. E. Articles by BUSECK, P. R. Search for Related Content

Off-axis electron holography of magnetotactic bacteria

¹ Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK E-mail: rafal.db@msm. cam. ac. uk
² Center for Solid State Science, Arizona State University, Tempe, Arizona 85287–1704, USA
³ Department of Earth and Environmental Sciences, University of Veszprém, Veszprém, POB 158, H-8201, Hungary
⁴ Department of Physics, California Polytechnic State University, San Luis Obispo, CA 93407, USA
⁵ Department of Microbiology, Immunology and Preventive Medicine, Iowa State University, Ames, IA 50011, USA
⁶ Departments of Geological Sciences and Chemistry/Biochemistry, Arizona State University, Tempe, AZ 85287-1404, USA

This paper was presented at the "Biogenic Iron Minerals" symposium held in Tihany, Hungary (May 2000)

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 50 nm 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 found to be constrained by magnetic interactions with adjacent, larger crystals in the chains. Magnetization reversal processes are followed in situ, allowing a coercive field of between 30 and 45 mT to be measured for the MV-1 cell. To within experimental error, the remanent magnetizations of the chains are found to be equal to the saturation magnetization of magnetite (0.60T). A new approach is used to determine that the magnetic moments of the chains are 7 and 5x10^–16Am² for the 1600-nm long MV-1 and 1200-nm long MS-1 chains examined, respectively. The degree to which the observed magnetic domain structure is reproducible between successive measurements is also addressed.

Key-words: magnetotactic bacteria, off-axis electron holography, magnetite nanocrystals, biologically controlled mineralization.

This article has been cited by other articles:

				T. Kasama, M. Posfai, R. K.K. Chong, A. P. Finlayson, P. R. Buseck, R. B. Frankel, and R. E. Dunin-Borkowski Magnetic properties, microstructure, composition, and morphology of greigite nanocrystals in magnetotactic bacteria from electron holography and tomography American Mineralogist, August 1, 2006; 91(8-9): 1216 - 1229. [Abstract] [Full Text] [PDF]

				B. Arato, Z. Szanyi, C. Flies, D. Schuler, R. B. Frankel, P. R. Buseck, and M. Posfai Crystal-size and shape distributions of magnetite from uncultured magnetotactic bacteria as a potential biomarker American Mineralogist, August 1, 2005; 90(8-9): 1233 - 1240. [Abstract] [Full Text] [PDF]

				M. R. McCARTNEY, U. LINS, M. FARINA, P. R. BUSECK, and R. B. FRANKEL Magnetic microstructure of bacterial magnetite by electron holography European Journal of Mineralogy, August 1, 2001; 13(4): 685 - 689. [Abstract] [Full Text] [PDF]