Engineering Cyanobacteria As Sustainable Biotechnology Platforms through Synthetic Biology Tools

Synthetic biology has demonstrated its ability to control metabolic functions through programmable biological devices.  Very few of these devices have been developed in photoautotrophs, but instead rely on heterotrophs.  Creating synthetic biology tools for cyanobacteria would enhance their utility as sustainable biotechnology platforms for the production of a wide range of important compounds.  In particular, synthetic transcriptional controllers can be employed to express metabolic and regulatory genes in precise amounts at a defined stage.  By tuning metabolic processes transcriptionally, production can be boosted as a result of 1) reducing the metabolic burden during the growth phase, 2) optimizing the generation of target compounds which may be toxic to the cells, and 3) regulating enzyme expression in response to the appropriate conditions.  Utilizing the fumarate and nitrate reduction system from Escherichia coli as an oxygen sensor for Synechocystis sp. PCC 6803, production of enzymes that are inactivated by oxygen can be transcriptionally coordinated with intracellular oxygen levels.  Inducible promoters that respond to exogenous compounds can also provide synthetic transcriptional control of many metabolic functions.  A variety of inducible promoters are used to engineer traditional hosts, but there are very few that function as desired in cyanobacteria, limiting the complexity of genetic programs that can be implemented.  We will present progress towards creating synthetic biology tools for cyanobacteria, including transcriptional regulation using our intracellular oxygen sensors and inducible promoters, to improve chemical production by Synechocystis sp. PCC 6803.