Wide-dynamic-range promoters engineered for cyanobacteria

Background: Cyanobacteria, prokaryotic cells with oxygenic photosynthesis, are excellent bioengineering targets to convert solar energy into solar fuels. Tremendous genetic engineering approaches and tools have been and still are being developed for prokaryotes. However, the progress for cyanobacteria is far behind with a specific lack of non-native inducible promoters. Results: We report the development of engineered TetR-regulated promoters with a wide dynamic range of transcriptional regulation. An optimal 239 (+/- 16) fold induction in darkness (white-light-activated heterotrophic growth, 24 h) and an optimal 290 (+/- 93) fold induction in red light (photoautotrophic growth, 48 h) were observed with the L03 promoter in cells of the unicellular cyanobacterium Synechocystis sp. strain ATCC27184 (i.e. glucose-tolerant Synechocystis sp. strain PCC 6803). By altering only few bases of the promoter in the narrow region between the -10 element and transcription start site significant changes in the promoter strengths, and consequently in the range of regulations, were observed. Conclusions: The non-native inducible promoters developed in the present study are ready to be used to further explore the notion of custom designed cyanobacterial cells in the complementary frameworks of metabolic engineering and synthetic biology.