A self-assembled micelle of a triblock copolymer, poloxamer 407, effectively forms a complex with N-acylhomoserine lactone (AHL) as a quorum-sensing (QS) signal in Gram-negative bacteria. The inhibitory effect of the poloxamer on QS in Serratia marcescens AS-1 enhanced at a concentration above a critical micelle concentration (CMC). The poloxamer micelle constitutes a novel class of QS regulator, which can activate the QS in AHLnegative strain S. marcescens AS-1S by the released AM, from AHL-loaded micelles added from outside.