pairing. Diaminopurine (Z) is an exception because it completely replaces adenine and
forms three hydrogen bonds with thymine in cyanophage S-2L genomic DNA. However, the
biosynthesis, prevalence, and importance of Z genomes remain unexplored. Here, we report
a multienzyme system that supports Z-genome synthesis. We identified dozens of globally
widespread phages harboring such enzymes, and we further verified the Z genome in one of …