Acylated homoserine lactones (AHLs) play a widespread role in intercellular communication
among bacteria. The Australian macroalga Delisea pulchra produces secondary metabolites
which have structural similarities to AHL molecules. We report here that these metabolites
inhibited AHL-controlled processes in prokaryotes. Our results suggest that the interaction
between higher organisms and their surface-associated bacteria may be mediated by
interference with bacterial regulatory systems.