The regulation of anthranilate synthesis for the production of pqs in pseudomonas aeruginosa

Abstract

The ubiquitous bacterium P. aeruginosa is an important human pathogen that causes devastating infections in immunocompromised patients and chronic infections in cystic fibrosis patients. The ability of P. aeruginosa to cause such debilitating infections is in part due to its three known cell-to-cell signals. The Pseudomonas quinolone signal (PQS, 2-heptyl-3-hydroxy-4-quinolone) is one of these intercellular signals and is required for virulence in multiple models of infection. The pathway needed for biosynthesis of PQS is also responsible for the production of at least 56 other 4-quinolone molecules. The synthesis of PQS, as well as the other 4-quinolone molecules, requires the condensation of anthranilate and a β-keto fatty acid. The precursor anthranilate is an important branch point molecule as it can be converted into PQS (or other metabolites), used for tryptophan synthesis, or catabolized as a carbon and nitrogen source. In P. aeruginosa, anthranilate is synthesized by either the breakdown of tryptophan through the kynurenine pathway or the conversion of chorismate via one of the two anthranilate synthases, TrpEG and PhnAB. The kynurenine pathway and the secondary anthranilate synthase PhnAB have been shown to provide anthranilate for the production of PQS. Our laboratory previously showed that the kynurenine pathway is the main source of anthranilate for PQS production in the presence of tryptophan, while PhnAB provides anthranilate under nutrient limiting conditions. In this work we aimed to gain a better understanding of the regulation of each of these metabolic routes to anthranilate. We described the transcriptional regulator KynR that is responsible for the upregulation of the kynurenine pathway genes in the presence of kynurenine. We also discovered that a single nucleotide change at nucleotide 1041 in pqsC resulted in a new transcript and the upregulation of pqsD, pqsE, and phnAB transcripts. This work provides insight into the regulation of anthranilate synthesis and the production of PQS.