title: Formation of tabular single-domain magnetite induced by Geobacter metallireducens GS-15.
abstract: Distinct morphological characteristics of magnetite formed intracellularly by magnetic bacteria (magnetosome) are invoked as compelling evidence for biological activity on Earth and possibly on Mars. Crystals of magnetite produced extracellularly by a variety of bacteria including Geobacter metallireducens GS-15, thermophilic bacteria, and psychrotolerant bacteria are, however, traditionally not thought to have nearly as distinct morphologies. The size and shape of extracellular magnetite depend on the culture conditions and type of bacteria. Under typical CO(2)-rich culture conditions, GS-15 is known to produce superparamagnetic magnetite (crystal diameters of approximately <30 nm). In the current study, we were able to produce a unique form of tabular, single-domain magnetite under nontraditional (low-CO(2)) culture conditions. This magnetite has a distinct crystal habit and magnetic properties. This magnetite could be used as a biosignature to recognize ancient biological activities in terrestrial and extraterrestrial environments and also may be a major carrier of the magnetization in natural sediments.
authors.affiliation: Department of Anatomy and Cell Biology and Facility for Electron Microscopy Research, McGill University, Montréal, QC, Canada H3A 2B2. vali@eps.mcgill.ca
authors.forename: Hojatollah
authors.initials: H
authors.lastname: Vali
authors.forename: Benjamin
authors.initials: B
authors.lastname: Weiss
authors.forename: Yi-Liang
authors.initials: YL
authors.lastname: Li
authors.forename: S Kelly
authors.initials: SK
authors.lastname: Sears
authors.forename: Soon Sam
authors.initials: SS
authors.lastname: Kim
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Kirschvink
authors.forename: Chuanlun L
authors.initials: CL
authors.lastname: Zhang
mesh_terms: D003460:Crystallization; D005290:Ferric Compounds; D005293:Ferritins / Q000737:chemistry / Q000378:metabolism; D052203:Ferrosoferric Oxide; D045302:Geobacter / Q000378:metabolism*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008280:Magnetics; D008854:Microscopy, Electron; D010087:Oxides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D005290:Ferric Compounds; D010087:Oxides; C092844:ferric oxyhydroxide; D005293:Ferritins; D007501:Iron; D052203:Ferrosoferric Oxide