Quorum sensing is a type of decision-making process used by decentralized groups to coordinate behavior. Many species of bacteria use quorum sensing to coordinate their gene expression according to the local density of their population by using small diffusible molecules that pass between neighboring cells. Cells can thus undergo communication. Similarly, some social insects use quorum sensing to make collective decisions. Some of the best-known examples of quorum sensing come from studies of bacteria. Quorum sensing can occur within a single bacterial species as well as among diverse species and can regulate a host of different processes, essentially serving as a simple communication network. Quorum sensing is a mechanism that ensures that sufficient cell numbers of a given species are present before eliciting a cell response. A variety of different molecules can be used as signals, such as lactones in Gram-negative bacteria or oligopeptides...