2-heptyl-3-hydroxy-4(1H)-Quinolone is a quorum-sensing signaling molecule produced by P. aeruginosa in response to increasing cell density.[1] It increases expression of the lasB gene, which encodes the virulence factor elastase, in P. aeruginosa (EC50 = ~30 μM in a reporter cell assay). 2-heptyl-3-hydroxy-4(1H)-Quinolone (60 μM) increases secretion of the metabolite pyocyanin and the lectin PA-IL, as well as increases biofilm production in P. aeruginosa populations.[2] It also reduces iron levels in P. aeruginosa growth media when used at a concentration of 40 μM and acts as an iron chelator in a Fe(III)-sulfate solution.[3]

Reference:
[1]. Pesci, E.C., Milbank, J.B.J., Pearson, J.P., et al. Quinolone signaling in the cell-to-cell communication system of Pseudomonas aeruginosa. Proc. Natl. Acad. Sci. USA 96(20), 11229-11234 (1999).
[2]. Diggle, S.P., Winzer, K., Chhabra, S.R., et al. The Pseudomonas aeruginosa quinolone signal molecule overcomes the cell density-dependency of the quorum sensing hierarchy, regulates rhl-dependent genes at the onset of stationary phase and can be produced in the absence of LasR. Mol. Microbiol. 50(1), 29-43 (2003).
[3]. Bredenbruch, F., Geffers, R., Nimtz, M., et al. The Pseudomonas aeruginosa quinolone signal (PQS) has an iron-chelating activity. Environ. Microbiol. 8(8), 1318-1329 (2006).