(704b) Engineered Quorum Sensing Systems for Protein Expression Regulation

A wildtype LuxI-LuxR quorum-sensing system enables autonomous activation of gene expression without the need of introducing inducing agents, a property particularly useful for industrial biotechnology and synthetic biology. However, the threshold cell density for activating gene expression is largely determined by the host genetic background and culture conditions. Such poor tunability exhibited by the wildtype system has significantly hampered its application in industrial microbiology. We have engineered the components of the LuxI-LuxR quorum-sensing system, and have used mutant components to construct highly tunable and auto-inducible systems for activation of gene expression at various cell densities. We further demonstrated the applications of these auto-inducible systems for the production of recombinant toxic proteins. By coupling with the Cre-loxP site-specific recombination system, tunable and auto-inducible deactivation of gene expression has also been achieved. Because this tunable and auto-inducible gene expression system enables choice of threshold cell densities for activating or deactivating gene expression, it is expected to be particularly useful for regulating gene expression in large-scale fermentations and synthetic biology.