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

Abstract

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 (AI‐1) and inhibited by 5500‐fold that of V. harveyi via of autoinducer 2 (AI‐2) as well as inhibited by 26 600‐fold the quorum sensing of E. coli via AI‐2; hence, this furanone is a non‐specific intercellular signal antagonist.