Characterization of Quorum Sensing in Cyanobacteria By Synthetic Circuit Controllers

Controlling the rate of gene expression has long been one of the principal aims of metabolic engineers. The applicability of systems with the ability to regulate metabolic flux range from medical therapies to industrial-scale chemical production. Specifically, the focus of this study will be to advance sustainable, specialty-chemical production without the use of petroleum-based reagents. Professor David Nielsen at Arizona State University has highlighted several strains of cyanobacteria with potential to be a tolerant host for the production of biofuels and other organics through the process of photosynthesis. The strain used in the following study is Cyanobacteria Synechococcus sp. PCC 7002 - a marine species with a high salt and light tolerance, low reliance on freshwater resources, and established processes for genetic modification. While 7002 is a strong candidate, it possesses a few of the historic bottlenecks that has prevented the use of heterologous metabolic pathways. One of the primary bottlenecks is the prevalence of self-toxic products that accumulate and harm the host cells. To prevent this, a phenomenon called quorum sensing - proven in other industrially tolerant microbes - can be used to stave off the conversion until the cell culture has reached an optimal growth rate. Quorum sensing is a form of dynamic expression which works by coupling an inducible promoter - driving a gene encoding for a conversion-dependent enzyme - to an inducer molecule that is also made by the cell. As the cell population increases, so does the concentration of this inducer molecule, driving the expression of the gene of interest (GOI). The following scheme is proposed in the figure attached, and more detail will be added about the proposed research plan if accepted. If the project is successful, quorum sensing will act as a key component in the genetic toolbox used to build a tolerant, sustainable, and productive industrial strain able to rival traditional petroleum fed processes.