Pseudomonas aeruginosa tRNA nucleotidyltransferase Cca controls resistance and tolerance to aminoglycoside antibiotics by regulating the MexXY multidrug efflux pump.

Pseudomonas aeruginosa 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 cca gene increases resistance and tolerance to aminoglycosides in P. aeruginosa. We demonstrate that the upregulation of mexXY genes contributes to the increased resistance and tolerance of the Δcca mutant. Furthermore, our experimental results revealed that Cca controls the transcription of armZ, which encodes a positive regulator of mexXY, through its leader peptide PA5471.1. An increased amount of PA5471.1 mRNA was found to be associated with ribosomes in the Δcca 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 armZ. Therefore, our data reveal the molecular mechanism of Cca-mediated regulation of aminoglycoside susceptibility in P. aeruginosa.