One of the long-term objectives of our research is to define the bacterial basis for biochemical and molecular events that characterize colonization of animal epithelial tissue. To accomplish this goal we have chosen as a model system the symbiotic infection of the light organ of the squid Euprymna scolopes by the luminous bacterium Vibrio fischeri. This system provides a simple, experimentally accessible, paradigm for studying specific, beneficial, host-bacterial interactions. Our recent investigations have centered on the events characterizing the initiation, colonization, and persistence of the symbiotic infection in newly hatched juvenile squids using bacterial mutants to manipulate and assay the complex succession of signaling and responses through which the host and bacterium communicate. Our recent completion of the V. fischeri genome project, and the construction of gene microarrays, has opened a new chapter in these studies.
We believe that this natural biological system serves as a model of pathogenic vibrio infection and, perhaps, of the evolution of the virulence state in vibrios; that is, bacterial and host determinants that potentiate light organ symbiosis may reveal convergences with known vibrio virulence factors, and promote the discovery of as yet undescribed ones. This work will also aid our understanding of the mechanisms by which benign colonizations of mollusk tissue serve as a reservoir for human pathogenic Vibrio species.