The iron-storage protein ferritin has been found in pennate diatoms—unicellular algae that are important in regulating oceanic carbon dioxide. Ferritin is used by a variety of organisms, including plants, animals, cyanobacteria, and other microorganisms, to concentrate and store iron. This is the first time that ferritin has been reported in the Stramenopiles family. There is no evidence that other Stramenopiles, including centric diatoms, produce ferritin. A team led by oceanographer E. Virginia Armbrust of the University of Washington, Seattle, identified ferritin proteins in the pennate diatoms Pseudo-nitzschia australis, P. multiseries, and P. granii (Nature, DOI: 10.1038/nature07539). The researchers solved a 1.95-Å-resolution crystal structure of the P. multiseries ferritin, a 530-kilodalton, 24-subunit protein. In an aerobic iron-uptake assay, a single protein bound more than 600 iron atoms. Under iron-limiting culture conditions, pennate diatoms that produce ferritin had a competitive advantage over centric diatoms that don't produce ferritin, suggesting that the protein may help some diatoms survive conditions when iron is in short supply.