HR: 1340h
AN: B33A-0840    [Abstracts]
TI: Magnetite Formation in Magnetospirillum Gryphiswaldense Studied With FORC Diagrams
AU: * Carvallo, C
EM: carvallo@impmc.jussieu.fr
AF: Institut de Minéralogie et de Physique des Milieux Condensés, Campus Boucicaut 140 rue de Lourmel, Paris, 75015, France
AU: Hickey, S
EM: stacha21@hotmail.com
AF: Institut de Minéralogie et de Physique des Milieux Condensés, Campus Boucicaut 140 rue de Lourmel, Paris, 75015, France
AU: Menguy, N
EM: menguy@impmc.jussieu.fr
AF: Institut de Minéralogie et de Physique des Milieux Condensés, Campus Boucicaut 140 rue de Lourmel, Paris, 75015, France
AU: Faivre, D
EM: damien.faivre@mpikg.mpg.de
AF: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials Research Campus Golm, Potsdam, 14424, Germany
AB: 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
DE: 0419 Biomineralization
DE: 1505 Biogenic magnetic minerals
DE: 1512 Environmental magnetism
DE: 1540 Rock and mineral magnetism
SC: Biogeosciences [B]
MN: 2007 Fall Meeting