Karas, B.J. et al. Nat. Commun. 6, 6925 (2015).

Diatoms, the beautiful, kaleidoscopic algae that make up a significant fraction of the world's phytoplankton, are important primary producers with potential as biofuels. Yet the study of these unique creatures, which are mainly unicellular and encased in silica walls, is hindered by poor genetic tools. Karas et al. now describe the first stable plasmid vector for diatoms. The plasmid contains a centromeric fragment from yeast that allows it to segregate into daughter cells with near-perfect efficiency. The authors use it to express proteins from the diverse diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. To transfer the episomes, they recruit Escherichia coli, providing the first evidence that bacteria can carry out cross-kingdom conjugation with diatoms and showing that it can be an effective means to deliver foreign DNA to these organisms.