Bacteria found to repurpose enzyme, build magnetic compass

Researchers at University of California, Berkeley have discovered that bacteria can repurpose a commonplace enzyme and use it as a scaffold on which to assemble iron atoms into tiny magnets.

With miniature magnets within themselves, the so-called magnetotactic bacteria are the ones able to navigate their environment using Earth's magnetic field as a reference.

Arash Komeili, an associate professor of plant and microbial biology, and his colleagues at UC Berkeley initially found the repurposing of a deactivated enzyme in one species, Magnetospririllum magneticum.

However, when the researchers looked throughout the three largest families of magnetotactic bacteria, they found independent occurrences of the same story.

"We really thought that something this unusual would have evolved only once," said graduate student David Hershey. "That just isn't the case. It really just cements how unusual this process is."

A key feature of building magnetic particles is a protease - an enzyme that chews up proteins for recycling - that is deactivated.

The findings, based on X-ray crystallographic images and reported in this week's issue of the journal PLOS Biology, suggest that the scaffold protein, called MamO, may guide iron atoms into position in the magnetite crystal lattice.

It demonstrates how evolution uses existing molecules for new functions.

The process for animals to build minerals is known as biomineralization. Magnetotactic bacteria, for example, snatch iron atoms and assemble them into magnetic nanoparticles, or tiny crystals of the mineral magnetite, that connect with their nervous system.

"We would like to know how minerals are built in nature since they constitute a fundamental survival strategy for many organisms," Komeili said.

Knowing what is going on with bacteria, researchers may one day use the tricks to build unique magnetic minerals in a test tube that are otherwise not possible. Endit