title: Magnetite Crystal Orientation in Magnetosome Chains.
abstract: One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to strong uniaxial shape anisotropy. Magnetosome chains in magnetotactic bacteria represent a biological paradigm of such magnet, where magnetite crystals synthesized in organelles called magnetosomes are arranged into linear chains. Two-dimensional synchrotron X-ray diffraction (XRD) is applied to cells of magnetotactic bacteria that are pre-aligned with a magnetic field to determine the crystallographic orientation of magnetosomes relative to the chain axis. The obtained pole figure patterns reveal a [111] fiber texture along the chain direction formagnetospirillastrains MSR-1 and AMB-1, whereas a [100] fiber texture is measured forDesulfovibrio magneticusstrain RS-1. The [100] axis appears energetically unfavorable because it represents a magnetic hard axis in magnetite, but can be turned into an effective easy axis by particle elongation along [100] for aspect ratios higher than 1.25, consistent with aspect ratios in RS-1 magnetosomes determined earlier. The pronounced fiber textures can be explained either by a strain-specific biological control on crystal orientation at the chain level or by physical alignment effects due to intra-chain magnetic interactions. In this case, biological control of the axis of elongation would be sufficient to influence the crystallographic texture of the magnetosome chain.
authors: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.
authors: André
authors: A
authors: Körnig
authors: Department of Earth and Environmental Sciences, Ludwig-Maximilians-University Munich Theresienstr. 41, 80333, Munich, Germany.
authors: Michael
authors: M
authors: Winklhofer
authors: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.
authors: Jens
authors: J
authors: Baumgartner
authors: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.
authors: Teresa Perez
authors: TP
authors: Gonzalez
authors: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.
authors: Peter
authors: P
authors: Fratzl
authors: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.
authors: Damien
authors: D
authors: Faivre
keywords: X-ray diffraction; magnetite; magnetosome chains; magnetotactic bacteria; texture patterns