MiaA-mediated tRNA modifications couple tryptophan attenuation and changes in tRNA abundance to complex phenotypes in Pseudomonas aeruginosa.

Transfer RNA (tRNA)-modifying enzymes are emerging as key regulators of bacterial physiology. MiaA, a tRNA isopentenyltransferase, is well studied in model organisms, but its role in the opportunistic pathogen Pseudomonas aeruginosa remains unclear. Using LC-MS, nanopore tRNA sequencing, as well as transcriptional, translational, and proteomic profiling, we mapped MiaA-dependent tRNA modifications and revealed unexpected effects of MiaA loss. Impaired translation of MiaA-sensitive codons reduced quorum-sensing-controlled virulence gene expression and attenuated pathogenicity in Galleria mellonella. Ribosome stalling at trp codons in miaA mutants overrides the attenuation-controlled repression of tryptophan biosynthesis, causing overproduction of tryptophan, along with upregulation of cognate tRNAs, thereby linking translation to global metabolic adaptation. MiaA is tightly regulated and is so central to bacterial physiology that its expression level correlates directly to virulence in clinical isolates, highlighting its role as a hub connecting translation, transcription, metabolism, and pathogenicity. These findings position MiaA as a key integrator of cellular processes critical for pathogen fitness and host interactions.