ABSTRACT
The regulation of virulence in phytopathogenic bacteria is essential for a successful infection. Pathogens must sense their surroundings and determine when, and equally importantly when not, to attack a host. Unnecessary virulence factor synthesis leads to an unrewarded cell metabolic load and may result in elimination of bacteria by the host defence systems. Sensing the presence of a susceptible host can occur through environmental factors such as osmolarity and nutrient availability. This sensing is achieved through a number of two-component phosphorelay systems and intracellular regulatory networks. Bacteria have also been shown to work together as communities, rather than discrete units, coordinating physiological functions, including the production of disease. This coordination occurs via a phenomenon called quorum sensing.
