magnetosome

[[File:Magnetite magnetosomes in Gammaproteobacteria.png |thumb |Magnetite magnetosomes in Gammaproteobacteria strain SS-5. (A) Chain of highly elongated magnetosomes. (B) Part of a magnetosome chain. (C) The magnetosome in the lower right in (B), viewed along the \scriptstyle [1\overline{1}0] direction, with its Fourier transform in the lower right.]] Magnetosomes are membranous structures present in magnetotactic bacteria (MTB). They contain iron-rich magnetic particles that are enclosed within a lipid bilayer membrane. Each magnetosome can often contain 15 to 20 magnetite crystals that form a chain which acts like a compass needle to orient magnetotactic bacteria in geomagnetic fields, thereby simplifying their search for their preferred microaerophilic environments. Recent research has shown that magnetosomes are invaginations of the inner membrane and not freestanding vesicles. Magnetite-bearing magnetosomes have also been found in eukaryotic magnetotactic algae, with each cell containing several thousand crystals.

Overall, magnetosome crystals have high chemical purity, narrow size ranges, species-specific crystal morphologies and exhibit specific arrangements within the cell. These features indicate that the formation of magnetosomes is under precise biological control and is mediated biomineralization.