ABSTRACT
Historically, bacteria have been studied as isolated organisms. It was appreciated that these organisms could detect and respond to their environment, such as responding with motility towards nutrients. Yet, the observation of various responses to stress, such as fruiting body formation in the myxobacteria, and the swarming motility seen in Proteus spp., suggested that bacteria were capable of coordinating their response and reacting as a population to a given environmental stimulus (1,2). Implicit in this belief was the presence of a mechanism for these organisms to communicate with each other. However, only recently has the level of complexity of these interactions become apparent. We now appreciate that simple single-celled organisms can express a complex array of different physiologies in response to their environment. Furthermore, it has become apparent that the single-celled organisms were not acting in isolation, but communicated with organisms of the same species as well as different species of bacteria. The hallmark of these communication systems is the evolution of a mechanism to transfer information from one cell to another using diffusible molecules.
