The magnetotactic bacteria have in common the ability to create nanomagnets that they use for detecting the earth’s magnetic poles. It is believed that their benefit for making the magnetic nanoparticles is the directional information they receive from the nanomagnets aligned as a compass. Using this directional information the cells can quickly identify points of the compass so that they can then identify the vertical axis that allows them to move up and down in their water environment. The advantage to the bacteria, which require a low oxygen environment for optimal metabolism, is to remain at the correct water level to support their metabolic needs. Our interest in magnetotactic bacteria is two-fold. First, many life forms, from bacteria to mammals, produce biominerals, but the molecular mechanisms for biomineralization are not well understood. Second, current methods for producing nanomagnets require high temperatures and the products are not the very reproducible. An understanding the molecular mechanisms by which bacteria control the production of nanomagnets could translate into better methods for producing nanomagnets for many high precision instruments and computer applications.
We are studying a protein called Mms6 that forms magnetic nanoparticles in vitro. Mms6 is a membrane protein that binds iron very tightly and also to high capacity. Our studies suggest that the mechanism by which Mms6 promotes the formation of magnetic nanoparticles involves high capacity binding and the ability of the protein to self-assemble into larger units that can provide platforms for iron assembly into the crystal units.