The Transcriptional Regulator CzcR Modulates Antibiotic Resistance and Quorum Sensing in Pseudomonas aeruginosa

Abstract

The opportunistic pathogen Pseudomonas aeruginosa responds to zinc, cadmium and cobalt by way of the CzcRS two-component system. In presence of these metals the regulatory protein CzcR induces the expression of the CzcCBA efflux pump, expelling and thereby inducing resistance to Zn, Cd and Co. Importantly, CzcR co-regulates carbapenem antibiotic resistance by repressing the expression of the OprD porin, the route of entry for these antibiotics. This unexpected co-regulation led us to address the role of CzcR in other cellular processes unrelated to the metal response. We found that CzcR affected the expression of numerous genes directly involved in the virulence of P. aeruginosa even in the absence of the inducible metals. Notably the full expression of quorum sensing 3-oxo-C12-HSL and C4-HSL autoinducer molecules is impaired in the absence of CzcR. In agreement with this, the virulence of the czcRS deletion mutant is affected in a C. elegans animal killing assay. Additionally, chromosome immunoprecipitation experiments allowed us to localize CzcR on the promoter of several regulated genes, suggesting a direct control of target genes such as oprD, phzA1 and lasI. All together our data identify CzcR as a novel regulator involved in the control of several key genes for P. aeruginosa virulence processes.

Genetic and phenotypic analysis of the GacS/GacA system in the moderate halophile Halomonas anticariensis

“…Nevertheless, AHL production was not fully restored when the gacS gene was complemented in trans in H. anticariensis FP35 T . The discrepancy found in correlating the AHL-defective phenotype shown by the gacS mutant with the corresponding complementation has been also reported in Pseudomonas aeruginosa where wild-type autoinducer levels were not restored in a TCS mutant complemented in trans by the sensor protein (Dieppois et al, 2012). Since RT-PCR analysis revealed a considerable decrease in the expression of the QS genes hanR and hanI compared with the wild-type strain, it would seem that these two systems are interlinked.…”

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

“…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.…”

“…CzcRS and CopRS are also involved in the downregulation of OprD expression with concomitant resistance to carbapenems (16,493). CzcR further affects various genes involved in virulence, including gene expression of quorum-sensing 3-oxo-C 12 -HSL and C4 -HSL autoinducers (386).…”

Investigating the host and bacterial factors in cystic fibrosis that promote persistence of infection in the lung

“…An observational study by Gray and colleagues, demonstrated increased concentrations of zinc and copper in the CF lung (216), and in separate in vitro studies these metals have been shown to induce P. aeruginosa resistance to carbapenem antibiotics (218). The origin of airway metal ions has not been determined, with potential sources including vascular leak, channelopathies and release from necrotic airway cells, or the bacteria themselves.…”