( Max Planck researchers uncover how a na...)Bacteria which sense the Earth's magnetic field

The entire bacterium is oriented like a compass needle inside the magnetic field. Until now, it was not clear how the cells organise magnetosomes into a stable chain, against their physical tendency to collapse by magnetic attraction. But using modern molecular-genetic and imaging processes, researchers from the Max Planck Institue for Marine Microbiology in Bremen and Max Planck Institute of Biochemistry in Martinsried, Germany have identified the protein responsible for creating the magnetosome chain. The scientists showed that this protein aligns the magnetosomes along a cytoskeletal structure which was previously unknown. This points to evidence that genetics regulate the magnetosome chain exactly. The structure is one of the most complex that has ever been found in bacterial cells. It is comparable to organelles that, until now, scientists had only been familiar with in higher organisms. (Nature, Advanced Online Publication, November 20, 2005).

Magnetotactic bacteria are widespread in the mud of marine environments. In their cell interior, they form magnetosomes which are aligned into a chain. The bacteria use them to distinguish "up" from "down" in the Earth's magnetic field, and navigate themselves confidently through layers of water to efficiently find optimal growth conditions. The magnetosomes are made of tiny crystals of the magnetic iron mineral magnetite (Fe3O4) -- only about 50 nanometres in size (one nanometre = one millionth of a millimetre).

To build magnetosomes, the cells do not only have to take up large amounts of iron from their surroundings and, from it, produce special iron oxide. The crystals also have to have a exactly defined number, form, and size, in order to be effective magnetic field sensors. To function optimally, the magnetosome crystals have to be strung into a straight chain inside the cell, t
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Source:Max-Planck-Gesellschaft