Effect of 2-BrHA, 2-BrOA and 2-BrDA on rhamnolipid production (blue halo test), swarming motility, and biofilm formation in P. aeruginosa strains PA14 and PAO1.

(A) Rhamnolipid production (note the arrow) was estimated by a conventional agar plate assay (blue halo test, the result for 2-BrHA only is shown). (B) In the swarming motility assay, PA14 or PAO1 was spotted on plates with either none (0 mM) or 5 mM 2-BrHA and grown at 30°C for 48 h. (C) Biofilm formation was assayed using the crystal violet method. Each bar represents a standard deviation averaging three independent samples. (D) The % inhibition of biofilm formation in the PA14 and PAO1 strains, calculated from the data in (C).