Archaea go multicellular under pressure

During the 3.5-billion-year history of life on Earth, some events, like the origin of life, of the eukaryotic cell, and of animals, occurred only once; however, the transition to multicellularity happened numerous times independently in slightly different ways. A recent census counted 45 independent such events in eukaryotes (1)—three of which gave rise to the respective ancestors of animals, land plants, and fungi (2). By contrast, multicellularity seems to be rare in Archaea—a group of prokaryotic microbes from which eukaryotes originated (3). On page 109 of this issue, Rados et al. (4) describe multicellular development in an archaeon, Haloferax volcanii, with an unexpected twist: Multicellularity is induced by mechanical pressure.