<i>Pseudomonas aeruginosa</i> tRNA nucleotidyltransferase Cca controls resistance and tolerance to aminoglycoside antibiotics by regulating the MexXY multidrug efflux pump

<i>Pseudomonas aeruginosa</i> displays high resistance to a wide range of antibiotics, greatly impeding clinical treatment. MexXY efflux pump plays an important role in bacterial resistance and tolerance to aminoglycoside antibiotics. tRNA nucleotidyltransferase (Cca, CCA-adding enzyme) is a universal polymerase responsible for the synthesis and repair of the 3'-terminal CCA sequence of tRNA. In this study, we found that mutation of the <i>cca</i> gene increases resistance and tolerance to aminoglycosides in <i>P. aeruginosa</i>. We demonstrate that the upregulation of <i>mexXY</i> genes contributes to the increased resistance and tolerance of the Δ<i>cca</i> mutant. Furthermore, our experimental results revealed that Cca controls the transcription of <i>armZ</i>, which encodes a positive regulator of <i>mexXY</i>, through its leader peptide PA5471.1. An increased amount of <i>PA5471.1</i> mRNA was found to be associated with ribosomes in the Δ<i>cca</i> mutant, indicating enhanced ribosome stalling. In addition, we found that the glutamine and phenylalanine at the third and fourth codons of PA5471.1, respectively, are involved in the Cca-mediated transcriptional upregulation of <i>armZ</i>. Therefore, our data reveal the molecular mechanism of Cca-mediated regulation of aminoglycoside susceptibility in <i>P. aeruginosa</i>.