Marine Biotech Fellowship: Molecular Analysis of Bacterial Genes Involved in Establishing the Vibrio Fischeri/Euprymna Scolopes Symbiotic Relationship

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9212452 GILSON The long term objective of this project is to understand the mechanisms involved in establishing a bacterial/animal symbiosis. Vibrio fischeri exists both as a free-living marine bacteria and as a bioluminescent inhabitant of the light organ of sepiolid squid and monocentrid fish. The association of V. fischeri and the small squid, Euprymna scolopes, offers a model mutualistic relationship and has already proven to be amenable to laboratory and molecular genetic methodologies. This project is directed at identifying the genes and gene products that are expressed as V. fischeri senses and responds to the conditions within the host. Genes that are expressed only when the bacteria is in association with the squid will be identified by fusions with a gene whose expression is essential for bacterial survival within the host, but, under selective conditions, is lethal outside the host. Protein gels (2-D) will be used to identify proteins that are preferentially synthesized in these two different environments. And since bioluminescence is preferentially exhibited under symbiotic conditions and is controlled by a density-dependent, pheromone-like molecule, other genes that are also part of this regulon will be identified through mudlac fusion technology. The relationship between V. fischeri and E. scolopes is apparently a mutualistic one, however its establishment and maintenance is evolutionarily related to commensal, parasitic and pathogenic associations. Information of the genetic basis for mechanisms of cell-cell communications, signal transduction and gene activation will be applicable to all of these systems. ***