The natural furanone ( 5Z )‐4‐bromo‐5‐(bromomethylene)‐3‐butyl‐2( 5H )‐furanone disrupts quorum sensing‐regulated gene expression in Vibrio harveyi by decreasing the DNA‐binding activity of the transcriptional regulator protein luxR

Abstract

Summary: This study aimed at getting a deeper insight in the molecular mechanism by which the natural furanone ( 5Z )‐4‐bromo‐5‐(bromomethylene)‐3‐butyl‐2( 5H )‐furanone disrupts quorum sensing in Vibrio harveyi . Bioluminescence experiments with signal molecule receptor double mutants revealed that the furanone blocks all three channels of the V. harveyi quorum sensing system. In further experiments using mutants with mutations in the quorum sensing signal transduction pathway, the compound was found to block quorum sensing‐regulated bioluminescence by interacting with a component located downstream of the Hfq protein. Furthermore, reverse transcriptase real‐time polymerase chain reaction with specific primers showed that there was no effect of the furanone on luxR Vh mRNA levels in wild‐type V. harveyi cells. In contrast, mobility shift assays showed that in the presence of the furanone, significantly lower levels of the LuxR Vh response regulator protein were able to bind to its target promoter sequences in wild‐type V. harveyi . Finally, tests with purified LuxR Vh protein also showed less shifts with furanone‐treated LuxR Vh , whereas the LuxR Vh concentration was found not to be altered by the furanone (as determined by SDS‐PAGE). Therefore, our data indicate that the furanone blocks quorum sensing in V. harveyi by rendering the quorum sensing master regulator protein LuxR Vh unable to bind to the promoter sequences of quorum sensing‐regulated genes.