is an opportunistic pathogen that causes a variety of acute and chronic infections. Usually a commensal on the host body, is capable of transforming into a virulent pathogen upon sensing favorable changes in the host immune system or stress cues. infections are hard to eradicate, because this pathogen has developed strong resistance to most conventional antibiotics; in addition, in chronic infections it commonly forms a biofilm matrix, which provides bacterial cells a protected environment to withstand various stresses including antibiotics. Given its importance as a human pathogen and its notorious antimicrobial tolerance, has been the subject of intensive investigations internationally. Research progress over the last two decades has unveiled a range of chemical communication systems in this pathogen. These diversified chemical communication systems endow a superb ability and remarkable flexibility to coordinate and modulate accordingly the transcriptional expression of various sets of genes associated with virulence and other physiologic activities in response to environmental changes. A fair understanding of the chemical signaling mechanisms with which governs virulence gene expression may hold the key to developing alternative therapeutic interventions that control and prevent bacterial infections.