Quorum-sensing antagonist (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)- furanone influences siderophore biosynthesis in Pseudomonas putida and Pseudomonas aeruginosa

Siderophore synthesis of Pseudomonas putida F1 was found to be regulated by quorum sensing since normalized siderophore production (per cell) increased 4.2-fold with cell density after the cells entered middle exponential phase; similarly, normalized siderophore concentrations in Pseudomonas aeruginosa JB2 increased 28-fold, and a 5.5-fold increase was seen for P. aeruginosa PAO1. Further evidence of the link between quorum sensing and siderophore synthesis of P. putida F1 was that the quorum-sensing-disrupter (5Z)-4-bromo-5- (bromomethylene)-3-butyl-2(5H)-furanone (furanone) from the marine red alga Delisea pulchra was found to inhibit the formation of the siderophore produced by P. putida F1 in a concentration-dependent manner, with 57% siderophore synthesis repressed by 100 μg/ml furanone. In contrast, this furanone did not affect the siderophore synthesis of Burkholderia cepacia G4 at 20-40 μg/ml, and stimulated siderophore synthesis of P. aeruginosa JB2 2.5- to 3.7-fold at 20-100 μg/ml. Similarly, 100 μg/ml furanone stimulated siderophore synthesis in P. aeruginosa PAO1 about 3.5-fold. The furanone appears to interact with the quorum-sensing machinery of P. aeruginosa PAO1 since it stimulates less siderophore synthesis in the P. aeruginosa qscR quorum-sensing mutant (QscR is a negative regulator of LasI, an acylated homoserine lactone synthase).