**3.1 Quorum sensing and its networks**

Quorum sensing bacteria produce and release chemical signal molecules termed autoinducers, whose external concentration increases as a function of increasing cell-population density. Once the bacteria detect that autoinducers have reached a minimal threshold level of stimulatory concentration, they will respond by altering their gene expression and behavior. Autoinducers are the cues by which QS bacteria communicate and synchronize particular behaviors on a population-wide scale, thus gaining the ability to function as a multicellular organism.
