Supplementary Material for “tRNA Modification Landscapes in Streptococci: Shared Losses and Clade-Specific Adaptations”

Transfer RNAs (tRNAs) help bacteria accurately read genetic information, but they require many chemical “modifications” to work properly. We mapped these modifications in two important human pathogens, Streptococcus mutans and Streptococcus pneumoniae, using genetics, chemistry, sequencing, and large-scale genome analysis. We found that both species have lost several modification pathways—especially those needing iron–sulfur enzymes—and that S. pneumoniae uses an unusual, shortened route to make the queuosine tRNA modification. We also discovered that a key tRNA modification is essential in S. pneumoniae but not in S. mutans. These differences reveal new insights into how pathogens adapt and may uncover future antibiotic targets.