In Pseudomonas aeruginosa the PA4203 gene, upstream of ppgL, encodes a LysR-type regulator similar to BenM and CatM in Acinetobacter spp. We described that the Pseudomonas aeruginosa ppgL (PA4204) gene, which encodes a protein with a signal peptide and with a COG2706 domain corresponding to a 3-carboxy-cis, cis-muconate lactonizing enzyme, could affect the fitness of P. aeruginosa. Cis,cis muconate is the effector for BenM and CatM, suggesting that the product of PA4204 could be the effector for PA4203 and could be a molecule similar to cis,cis muconate. Interestingly, a deletion of PA4203 affected the level of expression of ppgL and mexGHI-opmD. Furthermorethe PA4203 gene was highly expressed in a PA4204 mutant. This suggests that the product of PA4204 is the effector of the LysR regulator, which negatively regulates its own transcription. The PA4203 mutant grew like the wild-type, but did not produce the blue-green pigment pyocyanin on Pseudomonas P agar. Surprisingly, the same mutant was completely unable to produce the siderophore pyoverdine in CAA medium, but the production of the second siderophore, pyochelin, was not affected. The PA4203 mutant was hypomotile and also more sensitive to H2O2 compared to that of wild-type. Proteome analysis was done using 2D-PAGE with different staining methods (coomassie blue, silver staining, and DIGE). Cellular protein extracts of the PA4203 showed a low expression of some outer membrane proteins (OmpA) and extracellular chitinase. On the other hand, production of trigger factor, flagellin type B, the two component response regulator PhoP/Q and 50S ribosomal protein L9 were more pronounced in the PA4203 mutant. Secretome analysis showed that the production of two different types of the flagellar capping protein FliD and FliG in the PA4203 mutant versus WT, while the production of the chitin-binding protein CbpD precursor present in WT was not observed in the PA4203 mutant. The above results suggest that the LysR type regulator encoded by PA4203 is needed for the expression of ppgL (which is a modulator of quorum sensing) and mexGHI-opmD (which are part of the PQS regulon) and for the production of virulence factors.

Keywords