Researchers describe the full molecular structure of the phage DEV. DEV infects and lyses Pseudomonas aeruginosa bacteria, an opportunistic pathogen in cystic fibrosis and other diseases. DEV is part of an experimental phage cocktail developed to eradicate P. aeruginosa infection in pre-clinical studies. Bacterial viruses, known as phages, are the most abundant biological entities on the planet and are increasingly used as biomedicines to eradicate antibiotic-resistant pathogenic bacteria.