Magnetite Formation in Magnetospirillum Gryphiswaldense Studied With FORC Diagrams
Abstract
First-order reversal curve (FORC) diagrams, obtained from partial hysteresis curves, were measured on a set of cultured Magnetospirillum gryphiswaldense in order to study the formation of magnetite in magnetotactic bacteria. We used a cell-suspension assay for the growth-independent study of magnetite formation under highly controlled conditions. FORC diagrams showed a clear evolution from size distribution with a majority of superparamagnetic (SP) grains, to a distribution dominated by stable, single-domain grains, but still containing some SP particles. FORC diagrams also suggest that magnetostatic interactions increase during the formation and growth of the magnetite grains. TEM observations confirm this evolution. According to the saturation isothermal remanent magnetization (SIRM) cooling and warming curves, the Verwey transition can only be seen in the most mature samples, and well below 120 K. This suggests that the samples may have suffered from some partial oxidation
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFM.B33A0840C
- Keywords:
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- 0419 Biomineralization;
- 1505 Biogenic magnetic minerals;
- 1512 Environmental magnetism;
- 1540 Rock and mineral magnetism