Transporters Related to Stress Responses and Their Potential Application in Synechocystis sp. PCC 6803.

Cyanobacteria are autotrophic prokaryotes that can perform oxygenic photosynthesis. The conversion of light and carbon dioxide into green fuels and chemicals has drawn considerable interest, and several dozen products have been successfully synthesized in genetically engineered cyanobacteria. However, during cultivation, cyanobacterial cells are typically exposed to various stresses from the environment, such as acid, salt and metal stresses, as well as from the end products they synthesize, such as ethanol, butanol, and 3-hydroxypropionic acid (3-HP). These stresses hinder the accumulation of biomass and the production of chemicals or biofuels in cyanobacteria. Thus, improving the ability of cyanobacterial cells to resist stress can potentially enhance the robustness of the cyanobacterial chassis and the final yield of the target products. Toward this goal, research has been performed to explore the mechanisms by which cyanobacteria respond to various environmental perturbations and product toxicity. Among these mechanisms, transporters are membrane proteins involved in the transportation of ions, small molecules, or macromolecules across the membrane, and they have been reported to be involved in the response to common stresses in many organisms. Thus, engineering transporter-encoding genes may be a promising solution to increase the resistance of the cells against biotic and abiotic stresses. This chapter focuses on recent progress on the use of transporters related to stress responses in the model cyanobacterium Synechocystis sp. PCC 6803 and presents an updated review of their functions in stress regulation and their potential application in future chassis modifications.