Inhibition of biofilm formation and swarming of escherichia coli by (5Z)-4-bromo-5-(bromomethylene)-3- butyl-2(5H)-furanone

The quorum-sensing disrupter (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) of the alga Delisea pulchra was found to inhibit the swarming motility of Escherichia coli completely at 13 μg cm^-2 (also at 20 μg ml^-1) but did not inhibit its growth rate at 13-52 μg cm^-2 or from 20 to 100 μg ml^-1. Swimming was not inhibited by the furanone at 20-40 μg ml^-1. In addition, confocal scanning laser microscopy revealed that this furanone at 60 μg ml^-1 inhibited the biofilm formation of E. coli, as it decreased its thickness by 55%, reduced the number of water channels and decreased the percentage of live cells by 87%. This suggests that natural furanone may be used as a new method to control bacterial biofilms that does not involve toxicity. Furanone at 10 μg ml^-1 also inhibited by 3300-fold the quorum sensing of Vibrio harveyi via autoinducer 1 (Al-1) and inhibited by 5500-fold that of V. harveyi via of autoinducer 2 (Al-2) as well as inhibited by 26 600-fold the quorum sensing of E. coli via Al-2; hence, this furanone is a non-specific intercellular signal antagonist.