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 mug cm(-2) (also at 20 mug ml(-1)) but did not inhibit its growth rate at 13-52 mug cm(-2) or from 20 to 100 mug ml(-1). Swimming was not inhibited by the furanone at 20-40 mug ml(-1). In addition, confocal scanning laser microscopy revealed that this furanone at 60 mug 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 mug ml(-1) also inhibited by 3300-fold the quorum sensing of Vibrio harveyi via autoinducer 1 (AI-1) and inhibited by 5500-fold that of V. harveyi via of autoinducer 2 (AI-2) as well as inhibited by 26600-fold the quorum sensing of E. coli via AI-2; hence, this furanone is a non-specific intercellular signal antagonist.