Here are five key facts to understand about the breakthrough, published this week in the journal Science. The viruses only target bacteria, not humans, by designResearchers deliberately worked with bacteriophages, viruses that infect only bacteria, rather than pathogens capable of infecting humans, animals or plants. Bacteriophages have relatively small, comparatively simple genomes that are easier to synthesize and manipulate under controlled laboratory conditions. Only 16 of 300 tested genomes actually workedThe gap between AI-generated candidates and functional, real-world viruses proved enormous. The 16 successful viruses also behaved differently from one another, with some infecting bacteria more quickly and others showing varying replication abilities.