Quorum Sensing in Vibrio fischeri Cell Density-Dependent Activation of Symbiosis-Related Genes in a Marine Bacterium

The general objective of the proposed research is to fully elucidate the mechanism of quorum sensing and response in bacteria by continuing investigations of the most well-developed model for this phenomenon, autoinduction of lux genes in Vibrio fischeri. This research should continue to reveal general rules governing regulation of bacterial genes used specifically in symbiotic associations with marine animals. This research program also has recently provided and should continue to provide insights into how bacteria interact with eukaryotic hosts in a more universal way. Little is known about synthesis of the autoinducer, the sensory signal, other than that it is catalyzed by the luxI gene product. Thus, an analysis of the structure and function of LuxI was initiated. This analysis involved the construction of point and deletion mutations in luxI and studies of the activity of the mutant proteins encoded by these defective genes. This analysis also involved studies of autoinducer synthesis in luxI-containing E. coli amino acid biosynthesis mutants, and studies of the biochemistry of purified enzymes.