Wobbling Forth and Drifting Back: The Evolutionary History and Impact of Bacterial tRNA Modifications

Mol Biol Evol. 2018 Aug 1;35(8):2046-2059. doi: 10.1093/molbev/msy110.


Along with tRNAs, enzymes that modify anticodon bases are a key aspect of translation across the tree of life. tRNA modifications extend wobble pairing, allowing specific ("target") tRNAs to recognize multiple codons and cover for other ("nontarget") tRNAs, often improving translation efficiency and accuracy. However, the detailed evolutionary history and impact of tRNA modifying enzymes has not been analyzed. Using ancestral reconstruction of five tRNA modifications across 1093 bacteria, we show that most modifications were ancestral to eubacteria, but were repeatedly lost in many lineages. Most modification losses coincided with evolutionary shifts in nontarget tRNAs, often driven by increased bias in genomic GC and associated codon use, or by genome reduction. In turn, the loss of tRNA modifications stabilized otherwise highly dynamic tRNA gene repertoires. Our work thus traces the complex history of bacterial tRNA modifications, providing the first clear evidence for their role in the evolution of bacterial translation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria / genetics*
  • Base Composition
  • Biological Evolution*
  • Genome Size
  • Genome, Bacterial
  • RNA, Transfer / genetics
  • RNA, Transfer / metabolism*


  • RNA, Transfer