Amorphous mineral phases in magnetotactic multicellular aggregates

Magnetotactic multicellular aggregates consist of several bacteria that pro duce iron sulfide magnetosomes through a complex and poorly understood proc ess. We observed new amorphous mineral particles within the cytoplasm of ma gnetotactic multicellular aggregates. Elemental mapping and electron energy loss spectroscopy detected iron and oxygen, but not sulfur, in these parti cles. These amorphous particles were about the same size as mature magnetos omes, around 50-70 nm in diameter. No membranes were observed surrounding t he amorphous minerals. Partially crystalline inclusions composed of a cryst alline core and an amorphous region around them similar in texture to the a morphous particles were also present. The shape of these amorphous regions followed the shape of the crystalline cores they enveloped. These re-ions a lso contained oxygen and iron. The crystalline phase, as previously reporte d, contained sulfur and iron. The presence of independent amorphous particl es has not been reported before in magnetotactic multicellular aggregates.