Magnetism
Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron, nickel and cobalt and their alloys. The prefix "" refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, FeO.
Magnetosome
Magnetite crystals are encased in the magnetosome giving the MTB its magnetic properties. These crystals an either be made of iron oxide or sulfide. The MTB may either have iron oxide or sulfide but not both. Certain subgroups of the Proteobacteria in the domain of Bacteria have been found through analyses of the MTB’s RNA to only use iron oxide which is the more common material. Another smaller subdivision of the Proteobacteria that are part of a sulfide reducing bacteria use iron sulfide. Scientists say this suggests independent evolution of the same trait. The magnetite crystals have been observed in three different morphologies, cuboid, rectangular, and arrowhead shaped.