title: Elongated magnetite nanoparticle formation from a solid ferrous precursor in a magnetotactic bacterium.
abstract: Magnetotactic bacteria are aquatic microorganisms that intracellularly mineralize ferrimagnetic nanoparticles enabling the cells to align with the geomagnetic field. The bacteria produce a magnetic mineral of species-specific phase (magnetite Fe(II)Fe(III)2O4or greigite Fe(II)Fe(III)2S4), size, morphology and particle assembly. Several species produce crystals of unusual elongated particle shapes, which break the symmetry of the thermodynamically favoured isometric morphology. Such morphologies are thought to affect domain size and orientation of the internal magnetization. Therefore, they are interesting study objects to develop new synthetic strategies for the morphological control of nanoparticles. We investigate the formation of such irregularly shaped nanomagnets in the species Desulfovibrio magneticus RS-1. In contrast to previously described organisms, this bacterium accumulates iron predominantly as Fe(II) rather than Fe(III) consistent with an alternative oxidative biomineralization route. Further, using high-resolution electron microscopy, we observe an epitaxial relationship between precursor and the final mineral phase supporting the notion of a solid-state transformation pathway. The precursor is likely a green rust previously thought to convert to magnetite only by dissolution and re-precipitation. Our findings represent a novel observation in the interconversion of iron (oxyhydr)oxide materials and suggest that solid-state growth processes could be required to produce irregularly shaped, elongated magnetite nanocrystals.
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
authors.forename: Jens
authors.identifier: 0000-0002-5512-3249
authors.initials: J
authors.lastname: Baumgartner
authors.affiliation: Institut de Minéralogie et de Physique des Milieux Condensés, Unité Mixte de Recherche 7590 Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Institut de Recherches pour le Développement, Campus Jussieu, 75005 Paris, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Menguy
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
authors.forename: Teresa Perez
authors.initials: TP
authors.lastname: Gonzalez
authors.affiliation: Institut de Minéralogie et de Physique des Milieux Condensés, Unité Mixte de Recherche 7590 Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Institut de Recherches pour le Développement, Campus Jussieu, 75005 Paris, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Morin
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Widdrat
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany damien.faivre@mpikg.mpg.de.
authors.forename: Damien
authors.initials: D
authors.lastname: Faivre
mesh_terms: D003901:Desulfovibrio / Q000378:metabolism*; D052203:Ferrosoferric Oxide / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D058185:Magnetite Nanoparticles; D013440:Sulfides / Q000378:metabolism*
chemical_list: D058185:Magnetite Nanoparticles; D013440:Sulfides; C111959:greigite; D007501:Iron; D052203:Ferrosoferric Oxide
keywords: biomineralization; ferrous iron; magnetite; magnetotactic bacteria; precursor