Horizontally transferred genes with wide-ranging antibacterial properties may prove useful as new sources of antibiotic drugs, a study in eLife suggests. Metcalf et al. identified a bacterial lysozyme gene family with an unprecedented spread through horizontal gene transfer across the tree of life and diverse ecological contexts: the gene encoding glycosyl hydrolase 25 muramidase was found in a number of bacterial species, in eukaryotes (specifically in several fungal species, a plant and an insect) and in archaea (specifically in a single-cell microbe that lives in hot, deep-sea vents). Recombinant archaeal lysozyme exhibited broad-spectrum, dose-dependent antibacterial action. Moreover, when co-cultured with bacteria, lysozyme gene transcription was increased in the archaeon. This finding lends further support to the hypothesis that the transferred muramidase functions as a potent antibacterial molecule.