Pseudomonas aeruginosa is a wide-host-range gram negative opportunistic pathogen. To cause disease on hosts P. aeruginosa produces many virulence factors the production of which is under control of quorum sensing. Several genes were found in P. aeruginosa which can affect quorum sensing. in P. aeruginosa quorum sensing. This mutant could not grow like Wild Type (WT) in LB ( Luria Bertani) and CAA(Casamino acid) media and it had a delayed lag-phase (6h). The opmD mutant could not swarm, swim or twitch. It also produced low levels of 3-oxo-C12, C4-HSL and PQS compared to WT. Virulence factors such as pyoverdine and elastase were produced in lower amount and there was almost no production of pyocyanin. Virulence assay of the opmD mutant on excised chicory (Cichorium intybus) leaves showed rotted and necrotic areas on leaves which were ten times reduced compared to WT. There was however no significant difference in the expression of lasI and rhlI between opmD and WT but the expression of pqsA was lower than in the WT. Expression of oprM in mutant and WT was the same but oprN was not expressed in the opmD mutant. The transcription of the anthranilate dioxygenase genes antA and antB was undetectable in the opmD mutant. Cellular protein extracts of an opmD mutant showed a low expression of the outer membrane protein OprG versus WT and outer membrane proteins OprD, OprF, and extracellular chitinase were not detected in the opmD mutant. On the other hand, production of trigger factor, flagellin type B, the two component response regulator phoP and 50S ribosomal protein L9 were visible in the opmD and not in WT. Extracellular proteome analysis showed the production of two different types of the flagellar capping protein FliD in the opmD mutant versus WT, while the production of the chitin-binding protein CbpD precursor present in WT was not observed in the opmD mutant. The above results suggest that the opmD gene is important for P. aeruginosa to modulate quorum sensing and virulence.

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