Although the study of quorum sensing is relatively recent, it has been well established that bacteria produce, release, detect and respond to small signalling hormone-like molecules called "autoinducers". When a critical threshold concentration of the signal molecule is achieved, bacteria detect its presence and initiate a signalling cascade resulting in changes of target gene expression. Cell-cell communication has been shown within and between species with mechanisms substantially different in Gram-positive and Gram-negative bacteria. The identified quorum-sensing mechanisms in several food related Gram-negative and Gram-positive bacteria, including bacteriocin synthesis, luxS quorum sensing and interactions between sourdough starter lactic acid bacteria are reviewed. The understanding of extracellular signalling may provide a new basis for controlling over molecular and cellular process the deleterious and useful food related bacteria whose behaviour is mostly a consequence of very complex community interactions.