Ancient origin of cell death Gasdermins are cell death proteins in mammals that form membrane pores in response to pathogen infection. Johnson et al . report that diverse bacteria encode structural and functional homologs of mammalian gasdermins. Like their mammalian counterparts, bacterial gasdermins are activated by caspase-like proteases, oligomerize into large membrane pores, and defend against pathogen—in this case, bacteriophage—infection. Proteolytic activation occurs through the release of a short inhibitory peptide, and many bacterial gasdermins are lipidated to facilitate membrane pore formation. Pyroptotic cell death, a central component of mammalian innate immunity, thus has a shared origin with an ancient antibacteriophage defense system. —SMH