Synthesis of the bacterial magnetosome: the making of a magnetic personality.

Magnetotactic bacteria synthesize intracellular, enveloped, single magnetic domain crystals of magnetite (Fe3O4, Fe2+Fe2(3+)O4) and/or greigite (Fe3S4) called magnetosomes. The magnetosomes contain well-ordered crystals that have narrow size distributions and consistent species- and/or strain-specific morphologies. These characteristics are features of a process called biologically-controlled mineralization in which an organism exerts a great degree of crystallochemical control over the nucleation and growth of the mineral particle. Because of these features, the mineral particles have been used as biomarkers although not without controversy. These unique structures impart a permanent magnetic dipole moment to the cell causing it to align and swim along geomagnetic field lines, a behavior known as magnetotaxis. The apparent biological advantage of magnetotaxis is that it aids cells in more efficiently locating and maintaining position in vertical chemical gradients common in many natural aquatic environments.