The research in Dr. Greenberg’s laboratory is focused on the emerging field of sociomicrobiology. He is principally concerned with three aspects of sociomicrobiology: I. The biochemistry and molecular biology of environmental sensing and response in bacteria with a particular emphasis on a form of chemical communication between bacteria termed quorum sensing. II. The mechanisms by which bacteria switch from a nomadic existence to a sessile biofilm lifestyle and the mechanisms underlying the ability of biofilm bacteria to survive the action of antibiotics. III. The ways in which clonal populations of bacteria can discriminate themselves from other clonal populations. All of these phenomena are of importance in pathogenesis. Dr. Greenberg has concentrated much of his effort on Pseudomonas aeruginosa, an opportunistic pathogenic bacterium that can cause both acute and persistent biofilm infections. Quorum sensing allows certain bacterial species to monitor their own population density and respond by activating transcription of specific sets of genes. Current investigations of gene regulation in Pseudomonas aeruginosa serve as the model for this type of sensing system. The Greenberg lab is studying the binding of the signal to the receptor, the synthesis of the signal, the mechanism of gene activation by this chemical communication system, and the targets of quorum sensing control. Quorum sensing in P. aeruginosa is required for biofilm development and this has led to an effort to understand gene expression in biofilms. The Greenberg lab has identified key regulatory elements that define commitment steps in the development of biofilms and these serve as targets for novel antibiofilm therapeutic development.