Roles of bacterial regulators in the symbiosis between Vibrio fischeri and Euprymna scolopes.

In a symbiosis, two or more evolutionarily distinct organisms communicate with one another in order to co-exist and co-adapt in their shared environment. The mutualistic symbiosis between the bioluminescent marine bacterium Vibrio fischeri and the Hawaiian squid Euprymna scolopes provides a model system that allows scientists to examine the mechanisms by which this communication occurs (McFall-Ngai and Ruby 1991). The squid, although V. fischeri-free (aposymbiotic) at hatching, rapidly acquires this bacterium and promotes its growth in a special symbiotic organ called the light organ (LO). In exchange for nutrients and a niche safe from competing bacteria, V. fischeri provides the bioluminescence used by E. scolopes to camouflage itself from predators. In this chapter, we will give an overview of the early events in establishing the symbiosis and describe associated developmental changes triggered in each organism by the interaction. We will then discuss bacterial regulators and, where known, the traits they control that are necessary for a productive interaction between V. fischeri and E. scolopes. Finally, we will conclude by highlighting important directions for future investigation.