Vibrio fischeri " (2014). Doctoral Dissertations. Paper 481. Proteomic Characterization of Host-Microbe Interactions in the Euprymna scolopes Light Organ Symbiosis with Vibrio fischeri

The squid, Euprymna scolopes, and the bacterium, Vibrio fischeri, form a highly specific relationship that is used to study how beneficial bacteria interact with animal hosts. Even though the light organ of E. scolopes is exposed to the outside marine environment, it can only be colonized by V. fischeri. For this reason E. scolopes must carefully control the light organ microenvironment. One mechanism that the squid utilizes to regulate this symbiosis is a daily expulsion of V. fischeri from the light organ. The squid expels the symbiont, in addition to some host tissue, as a thick exudate that was collected and analyzed by high-throughput mass spectrometry (MS)-based proteomics. As expected, many of the V. fischeri proteins identified exemplify the lifestyle of the symbiont in the light organ including quorum sensing and the management of oxidative stress. The function of one of the V. fischeri proteins identified, a bacterial immunoglobulin-like surface protein, was further characterized by creating a mutant deficient in this protein. Host proteins within the light organ also highlighted the oxidative microenvironment, but proteins associated with innate immunity were prominent as well. The innate immune response, including macrophage-like hemocytes, of E. scolopes is considered t