Growth Inhibitory Levels of Salicyclic Acid Decrease Pseudomonas aeruginosa fliC Flagellin Gene Expression

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen that forms recalcitrant biofilms. It has previously been observed that biofilm formation in P. aeruginosa can be attenuated by the addition of salicylic acid (SA). As cellular motility is involved in biofilm formation, this study investigated whether salicylic acid could affect the expression of fliC which produces flagellin, an important component of the flagella required for motility. Turbidity measurements and luminescence assay conducted on parent strain P. aeruginosa PAO1 and the derivative H1001 strain containing a fliC:: luxCDABE reporter construct showed stasis in turbidity and a significant decrease in substrate-dependent luciferase activity when treated with 50 mM salicylic acid. Phase contrast microscopy observation also correlated the loss of motility in the P. aeruginosa PAO1 and H1001 strain with SA treatment at 50 mM. These results suggest that the salicylic acid may inhibit motility and cell growth by decreasing fliC expression.