Evolution of Translation Machinery

The translation machinery (TM) is one of life's oldest and most conserved molecular machineries. The “extended complexity hypothesis” posits that the TM's evolvability is constrained by its high complexity, i.e. the large number of interacting components making up the machine, leading to high evolutionary conservation across the tree of life. On the other hand, TMs can adapt under strong selection such as antibiotics while preserving functionality, which suggests that this high complexity does not eliminate its ability to adaptively evolve. Here we probe TM evolvability by replacing the elongation factor Tu (EF-Tu) native to Escherichia coli with its orthologs from other bacteria and subjecting these strains to laboratory evolution. We find evidence for rapid TM adaptation as well as ortholog-specific adaptive events in native TM proteins. While the TM can evolve rapidly despite its complexity, the adaptive responses are canalized towards a small number of genotype-specific target genes.