[Show abstract][Hide abstract] ABSTRACT: Pseudomonas aeruginosa is a Gram-negative bacterium that is ubiquitous in the environment, and it is an opportunistic pathogen that can infect a
variety of hosts, including humans. During the process of infection, P. aeruginosa coordinates the expression of numerous virulence factors through the production of multiple cell-to-cell signaling molecules.
The production of these signaling molecules is linked through a regulatory network, with the signal N-(3-oxododecanoyl) homoserine lactone and its receptor LasR controlling the induction of a second acyl-homoserine lactone
signal and the Pseudomonas quinolone signal (PQS). LasR-mediated control of PQS occurs partly by activating the transcription of pqsR, a gene that encodes the PQS receptor and is necessary for PQS production. We show that LasR interacts with a single binding
site in the pqsR promoter region and that it does not influence the transcription of the divergently transcribed gene, nadA. Using DNA affinity chromatography, we identified additional proteins that interact with the pqsR-nadA intergenic region. These include the H-NS family members MvaT and MvaU, and CysB, a transcriptional regulator that controls
sulfur uptake and cysteine biosynthesis. We show that CysB interacts with the pqsR promoter and that CysB represses pqsR transcription and PQS production. Additionally, we provide evidence that CysB can interfere with the activation of pqsR transcription by LasR. However, as seen with other CysB-regulated genes, pqsR expression was not differentially regulated in response to cysteine levels. These findings demonstrate a novel role for CysB
in influencing cell-to-cell signal production by P. aeruginosa.
IMPORTANCE The production of PQS and other 4-hydroxy-2-alkylquinolone (HAQs) compounds is a key component of the P. aeruginosa cell-to-cell signaling network, impacts multiple physiological functions, and is required for virulence. PqsR directly regulates
the genes necessary for HAQ production, but little is known about the regulation of pqsR. We identified CysB as a novel regulator of pqsR and PQS production, but, unlike other CysB-controlled genes, it does not appear to regulate pqsR in response to cysteine. This implies that CysB functions as both a cysteine-responsive and cysteine-unresponsive regulator
in P. aeruginosa.
Full-text · Article · Apr 2015 · Journal of bacteriology
[Show abstract][Hide abstract] ABSTRACT: The opportunistic pathogen Pseudomonas aeruginosa can utilize a variety of carbon sources and produces many secondary metabolites to help survive harsh environments. P. aeruginosa is part of a small group of bacteria that use the kynurenine pathway to catabolize tryptophan. Through the kynurenine pathway,
tryptophan is broken down into anthranilate, which is further degraded into tricarboxylic acid cycle intermediates or utilized
to make numerous aromatic compounds, including the Pseudomonas quinolone signal (PQS). We have previously shown that the kynurenine pathway is a critical source of anthranilate for PQS
synthesis and that the kynurenine pathway genes (kynA and kynBU) are upregulated in the presence of kynurenine. A putative Lrp/AsnC-type transcriptional regulator (gene PA2082, here called
kynR), is divergently transcribed from the kynBU operon and is highly conserved in Gram-negative bacteria that harbor the kynurenine pathway. We show that a mutation in kynR renders P. aeruginosa unable to utilize l-tryptophan as a sole carbon source and decreases PQS production. In addition, we found that the increase of kynA and kynB transcriptional activity in response to kynurenine was completely abolished in a kynR mutant, further indicating that KynR mediates the kynurenine-dependent expression of the kynurenine pathway genes. Finally,
we found that purified KynR specifically bound the kynA promoter in the presence of kynurenine and bound the kynB promoter in the absence or presence of kynurenine. Taken together, our data show that KynR directly regulates the kynurenine
Full-text · Article · Sep 2011 · Journal of bacteriology
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas aeruginosa is an opportunistic human pathogen which relies on several intercellular signaling systems for optimum population density-dependent
regulation of virulence genes. The Pseudomonas quinolone signal (PQS) is a 3-hydroxy-4-quinolone with a 2-alkyl substitution which is synthesized by the condensation of
anthranilic acid with a 3-keto-fatty acid. The pqsABCDE operon has been identified as being necessary for PQS production, and the pqsA gene encodes a predicted protein with homology to acyl coenzyme A (acyl-CoA) ligases. In order to elucidate the first step
of the 4-quinolone synthesis pathway in P. aeruginosa, we have characterized the function of the pqsA gene product. Extracts prepared from Escherichia coli expressing PqsA were shown to catalyze the formation of anthraniloyl-CoA from anthranilate, ATP, and CoA. The PqsA protein
was purified as a recombinant His-tagged polypeptide, and this protein was shown to have anthranilate-CoA ligase activity.
The enzyme was active on a variety of aromatic substrates, including benzoate and chloro and fluoro derivatives of anthranilate.
Inhibition of PQS formation in vivo was observed for the chloro- and fluoroanthranilate derivatives, as well as for several
analogs which were not PqsA enzymatic substrates. These results indicate that the PqsA protein is responsible for priming
anthranilate for entry into the PQS biosynthetic pathway and that this enzyme may serve as a useful in vitro indicator for
potential agents to disrupt quinolone signaling in P. aeruginosa.
Full-text · Article · Mar 2008 · Journal of bacteriology