Quorum sensing describes the small molecule signaling mechanism that bacteria use to coordinate population-level behaviors.  Bacterial expression of these behaviors can significantly impact the health of their host.  The marine bacterium Vibrio fischeri colonizes specific sites in the Hawaiian Squid Euprymna scolopes, forming a mutually beneficial symbiosis where the V. fischeri populations produce bioluminescence through quorum sensing.  This symbiosis serves as a model system to study quorum sensing within a host environment.