The Regulatory Repertoire of Pseudomonas aeruginosa AmpC ß-Lactamase Regulator AmpR Includes Virulence Genes

Abstract

In Enterobacteriaceae , the transcriptional regulator AmpR, a member of the LysR family, regulates the expression of a chromosomal β-lactamase AmpC. The regulatory repertoire of AmpR is broader in Pseudomonas aeruginosa , an opportunistic pathogen responsible for numerous acute and chronic infections including cystic fibrosis. In addition to regulating ampC , P. aeruginosa AmpR regulates the sigma factor AlgT/U and production of some quorum sensing (QS)-regulated virulence factors. In order to better understand the ampR regulon, we compared the transcriptional profile generated using DNA microarrays of the prototypic P. aeruginosa PAO1 strain with its isogenic ampR deletion mutant, PAOΔ ampR . Transcriptome analysis demonstrates that the AmpR regulon is much more extensive than previously thought, with the deletion of ampR influencing the differential expression of over 500 genes. In addition to regulating resistance to β-lactam antibiotics via AmpC, AmpR also regulates non-β-lactam antibiotic resistance by modulating the MexEF-OprN efflux pump. Other virulence mechanisms including biofilm formation and QS-regulated acute virulence factors are AmpR-regulated. Real-time PCR and phenotypic assays confirmed the microarray data. Further, using a Caenorhabditis elegans model, we demonstrate that a functional AmpR is required for P. aeruginosa pathogenicity. AmpR, a member of the core genome, also regulates genes in the regions of genome plasticity that are acquired by horizontal gene transfer. Further, we show differential regulation of other transcriptional regulators and sigma factors by AmpR, accounting for the extensive AmpR regulon. The data demonstrates that AmpR functions as a global regulator in P. aeruginosa and is a positive regulator of acute virulence while negatively regulating biofilm formation, a chronic infection phenotype. Unraveling this complex regulatory circuit will provide a better understanding of the bacterial response to antibiotics and how the organism coordinately regulates a myriad of virulence factors in response to antibiotic exposure.

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

“…Both AmpG and AmpP are inner membrane permeases with 14 and 10 transmembrane helices, respectively [151]. The expression of ampG and ampP is regulated by the transcriptional regulator AmpR (PA4109) in an inducer (sub-MIC of b-lactam)-dependent and -independent manner, respectively [18]. Both ampG and ampP are the second genes in independent two-gene operons [151].…”

“…We discuss the roles of the genes involved in cell-wall synthesis and recycling in conferring resistance to both b-lactam and non-b-lactam antibiotics. The review also focuses on the global regulator AmpR that connects cell-wall recycling to other resistance mechanisms through its diverse regulatory role in P. aeruginosa [18,19].…”

The β-Lactamase Gene Regulator AmpR Is a Tetramer That Recognizes and Binds the d-Ala-d-Ala Motif of Its Repressor UDP-N-acetylmuramic Acid (MurNAc)-pentapeptide

“…The genes encoding AmpC and AmpR form a divergent operon (ampR-ampC), which allows AmpR to bind to overlapping promoters within the intergenic region of the operon to control the transcription of both genes (2). Moreover, AmpR has also been found to exert transcriptional control over an additional chromosomal class D ␤-lactamase gene as well as numerous virulence-associated genes in P. aeruginosa (3,4). Accordingly, there has been an increased interest to better understand how AmpR regulates gene expression.…”

Antimicrobial Effect of Imipenem-Functionalized Fe2O3 Nanoparticles on Pseudomonas aeruginosa Producing Metallo b-lactamases

“…Inactivity of porin cahnnels (OprD) in one hand and the activity of beta lactamases (AmpC) related to chromosome, in the others seems the causative agents of high resistance towards imipenem (10)(11)(12). Furthermore, the role of antibiotic efflux pumps align with the production of metallo-beta-lactamases can both contribute to the resistance towards carbapenems (13,14).…”