Methods are provided for identifying molecules that can be used to positively and negatively manipulate quorum-sensing-mediated communication to control bacterial behavior. Small-molecule antagonists that disrupt quorum-sensing-mediated activities are identified. Methods are provided for disrupting detection of acyl-homoserine lactone autoinducer in Gram-negative bacteria by contacting the bacteria with the antagonists. Methods of inhibiting quorum sensing-mediated activity in Gram-negative bacteria are provided wherein the activity is pathogenicity, bioluminescence, siderophore production, type III secretion, or metalloprotease production.
