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

ABSTRACT 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 Δ cca 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 Δ cca 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 .