Biomineralization has long been recognized as an important albeit not always appreciated process in microbiology. Too bad, because microbes have literally made mountains. They have formed huge rock deposits, such as the celebrated White Cliffs of Dover, these being the accumulation of calcium carbonate shells of the alga, Emiliania huxleyi. As with these carbonate shells, microorganisms most often deposit such minerals extracellularly. For other examples discussed in this blog, click here and here.
Only in rare cases are minerals accumulated within microbes. The iron-containing magnetic inclusions called magnetosomes made by magnetotactic bacteria are one example of such intracellular biomineralization. Forming these ‘biomagnets’ within the cell makes sense, as it enables the cell to orient itself in a magnetic field. The sulfur bacteria also deposit their sulfur-storage granules intracellularly. That has been pretty much it for mineral inclusions within bacteria, until the recent discovery of calcified microcannonball-like bodies inside a new species of cyanobacteria. It’s nothing like anything you’ve seen before.
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