A family of bacteriophages uses an expanded genetic alphabet

Bacteriophage genomes are the richest source of modified nucleobases of any life form. Of these, 2,6-diaminopurine (2-aminoadenine) that pairs with thymine by forming three hydrogen bonds is the only one violating Watson and Crick's base pairing. 2,6-diaminopurine (2-aminoadenine), initially found in the cyanophage S-2L, is more widespread than expected and has also been detected in bacteriophage infecting Gram-negative and Gram-positive bacteria. The biosynthetic pathway for aminoadenine containing DNA as well as the exclusion of adenine are now elucidated. This example of a natural deviation from the DNA canonical nucleotides represents only one of the possibilities explored by nature and provides a proof of concept for the synthetic biology of non-canonical nucleic acids.