Global reprogramming of virulence and antibiotic resistance in Pseudomonas aeruginosa by a single nucleotide polymorphism in elongation factor, fusA1

Eve A Maunders,Rory C Triniman,Joshua Western,Taufiq Rahman,Martin Welch

doi:10.1074/jbc.ra119.012102

Eve A Maunders, Rory C Triniman + Show 3 more

Open Access

https://doi.org/10.1074/jbc.ra119.012102

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Abstract

Clinical isolates of the opportunistic pathogen Pseudomonas aeruginosa from patients with cystic fibrosis (CF) frequently contain mutations in the gene encoding an elongation factor, FusA1. Recent work has shown that fusA1 mutants often display elevated aminoglycoside resistance due to increased expression of the efflux pump, MexXY. However, we wondered whether these mutants might also be affected in other virulence-associated phenotypes. Here, we isolated a spontaneous gentamicin-resistant fusA1 mutant (FusA1P443L) in which mexXY expression was increased. Proteomic and transcriptomic analyses revealed that the fusA1 mutant also exhibited discrete changes in the expression of key pathogenicity-associated genes. Most notably, the fusA1 mutant displayed greatly increased expression of the Type III secretion system (T3SS), widely considered to be the most potent virulence factor in the P. aeruginosa arsenal, and also elevated expression of the Type VI (T6) secretion machinery. This was unexpected because expression of the T3SS is usually reciprocally coordinated with T6 secretion system expression. The fusA1 mutant also displayed elevated exopolysaccharide production, dysregulated siderophore production, elevated ribosome synthesis, and transcriptomic signatures indicative of translational stress. Each of these phenotypes (and almost all of the transcriptomic and proteomic changes associated with the fusA1 mutation) were restored to levels comparable with that in the progenitor strain by expression of the WT fusA1 gene in trans, indicating that the mutant gene is recessive. Our data show that in addition to elevating antibiotic resistance through mexXY expression (and also additional contributory resistance mechanisms), mutations in fusA1 can lead to highly selective dysregulation of virulence gene expression.

Highlights

Due to its high intrinsic resistance to antibiotics and aggressive virulence, Pseudomonas aeruginosa holds the dubious accolade of consistently occupying a “top ten” slot on lists of clinical threats across the globe
The function of the P. aeruginosa Type VI (T6) secretion system has become clearer in the last decade; it appears to play a role in killing other bacterial species [8, 9], especially in tightly packed biofilms where competition for the same resources is rife
We showed that the rapidly growing planktonic cells associated with increased virulence factor production display markedly up-regulated expression of the machinery required for macromolecular synthesis, especially proteins involved in translation [14]

Summary

Introduction

Due to its high intrinsic resistance to antibiotics and aggressive virulence, Pseudomonas aeruginosa holds the dubious accolade of consistently occupying a “top ten” slot on lists of clinical threats across the globe. The substantial growth defect associated with EMC1 grown in LB was complementable by expression of the WT fusA1 gene in trans on a plasmid (Fig. S2), suggesting that the WT allele is dominant. This suggests that the GmR phenotype conferred by these other mutated fusA1 proteins is not linked with PcrV expression.

Results

Conclusion