[biorxiv.org] We evaluate whether tryptophan (W), widely thought to be the last of the 20 canonical amino acids added to the genetic code, was already present in the Last Universal […]
![Recombination transferred part of archaeal YRS into non-canonical bacterial YRS. A) YRS core catalytic domain alignment from archaeal (indicated left as blue), bacterial non-canonical (purple) and bacterial canonical (pink) sequences. Both recombinant and nonrecombinant YRSs are found within all four major bacterial supergroups (Terrabacteria, Proteobacteria, PVC and FCB) B) Speciestree reconciled consensus trees reconstructed for the non-recombinant (left) and recombinant YRS sites (right). Branch lengths were estimated using NQ.bac+R10 in IQ-Tree v2.1.332. -- [biorxiv.org]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Tryptophan-became.png?resize=1200%2C720&ssl=1)
[biorxiv.org] We evaluate whether tryptophan (W), widely thought to be the last of the 20 canonical amino acids added to the genetic code, was already present in the Last Universal […]