Transcriptome profiling reveals links between ParS/ParR, MexEF-OprN, and quorum sensing in the regulation of adaptation and virulence in Pseudomonas aeruginosa

Abstract

BackgroundThe ParS/ParR two component regulatory system plays critical roles for multidrug resistance in Pseudomonas aeruginosa. It was demonstrated that in the presence of antimicrobials, ParR enhances bacterial survival by distinct mechanisms including activation of the mexXY efflux genes, enhancement of lipopolysaccharide modification through the arn operon, and reduction of the expression of oprD porin.ResultsIn this study, we report on transcriptomic analyses of P. aeruginosa PAO1 wild type and parS and parR mutants growing in a defined minimal medium. Our transcriptomic analysis provides the first estimates of transcript abundance for the 5570 coding genes in P. aeruginosa PAO1. Comparative transcriptomics of P. aeruginosa PAO1 and par mutants identified a total of 464 genes regulated by ParS and ParR. Results also showed that mutations in the parS/parR system abolished expression of the mexEF-oprN operon by down-regulating the regulatory gene mexS. In addition to the known effects on drug resistance genes, transcript abundances of the quorum sensing genes (rhlIR and pqsABCDE-phnAB) were higher in both parS and parR mutants. In accordance with these results, a significant portion of the ParS/ParR regulated genes belonged to the MexEF-OprN and quorum sensing regulons. Deletion of the par genes also led to increased phenazine production and swarming motility, consistent with the up-regulation of the phenazine and rhamnolipid biosynthetic genes, respectively.ConclusionOur results link the ParS/ParR two component signal transduction system to MexEF-OprN and quorum sensing systems in P. aeruginosa. These results expand our understanding of the roles of the ParS/ParR system in the regulation of gene expression in P. aeruginosa, especially in the absence of antimicrobials.

The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

“…However, the functional link between MexS and MexEF-OprN might be more complex than anticipated, as data suggest that overexpressed mexS would also lead to MexTdependent mexEF-oprN overexpression, at least in certain genetic backgrounds (850). Moreover, mutations in the ParSR system, which is involved in the regulation of MexXY, downregulate the expression of both mexS and mexEF-oprN (387). Interestingly, concomitant upregulation of MexS and MexEF-OprN was seen when P. aeruginosa was exposed to airway epithelial cells releasing unknown efflux-inducing signals (851).…”

“…On the other hand, P. aeruginosa possesses specific channels, such as OprB, specific for glucose uptake, and OprD, specific for the diffusion of basic amino acids and peptides (22). The latter channel is the primary channel for the entry of carbapenems across the OM, and the reduced expression or loss of OprD has been frequently observed in carbapenem-resistant clinical isolates (379)(380)(381)(382)(383)(384), which may also display upregulated drug efflux systems, such as MexEF-OprN, due to the shared regulation of the expression of OprD and MexEF-OprN (carbapenem susceptibility is unlikely affected by MexEF-OprN) (see Regulation of Multidrug Efflux Pumps, below) (385)(386)(387). RND efflux pumps.…”

Nosocomial infection and its molecular mechanisms of antibiotic resistance

“…At the same time, MexT downregulates oprD at the transcriptional and translational levels, leading to a decreased amount of OprD (80). On the other hand, loss of MexS, a supposed oxidoreductase/ dehydrogenase, has been thought to lead to formation of secondary metabolites which may serve as effecters for MexT (77). These effecters could combine with MexT, change the structure of the regulatory protein, and alter MexT into an activating situation.…”

“…One of the most important regulatory mechianisms is the coincident overproduction of the MexEF-OprN efflux pump and downregulation/upregulation of the OprD porin (77). In wild P. aeruginosa, MexT is silenced owing to either the existence of repressing mutations or the deficiency of a secondary effecter (78).…”

RNA Sequencing Analysis of the Broad-Host-Range Strain Sinorhizobium fredii NGR234 Identifies a Large Set of Genes Linked to Quorum Sensing-Dependent Regulation in the Background of a traI and ngrI Deletion Mutant

“…However, only a few studies so far have used this technology for the genome-wide analysis of QS-dependent expression profiles. The focus of these studies was on the opportunistic pathogenic microorganism Burkholderia cenocepacia (26) and on Pseudomonas aeruginosa (27,28). Interestingly, no study has yet focused on the QS-dependent gene regulation in sinorhizobia or closely related species using RNA-seq.…”