In quorum sensing, bacteria produce and respond to small signal molecules allowing for the activation of coordinated cellular behavior that is dependent on cell population density. Quorum-sensing systems are composed of two components: a signal synthase, and a transcription factor activated by the signal molecule. Through the directed evolution of LuxR, the transcription factor from the LuxI-LuxR quorum-sensing system, we are looking to create a library of LuxI-LuxR systems that activate at different cellular densities. These engineered systems will then be used for applications in synthetic biology. The usefulness of quorum-sensing systems in synthetic biology has already been shown, and we aim to further demonstrate their utility by using our engineered library for the construction of unique and optimized synthetic constructs. This presentation will detail the directed evolution procedure used to obtain the mutant LuxR proteins, and show their implementation in two systems of interest to synthetic biology.