Inducible expression system for the marine cyanobacterium Synechococcus sp. strain NKBG 15041c

Cyanobacteria have been recognized as promising host organisms to produce biofuel materials including hydrogen and hydrocarbons due to high biomass productivity and capability of transformation. Metabolic engineering has recently been employed for further enhancement of bioenergy production, while excess fuel materials could give rise to cytotoxicity. Therefore genetic tools are required in order to precisely control the gene expression involved in the fuel production metabolism. Thus far, inducible-expression systems in cyanobacteria have been established mainly in freshwater strains. However there are a few reports with regard to marine strains, which can use vast of ocean for cultivation. In this study, we established a tetracycline-inducible gene expression system in the marine cyanobacterium Synechococcus sp. strain NKBG 15041c. Since tetracycline-inducible system is a non-native regulation, it is expected for inherent metabolisms not to be disrupted. The de novo designed promoter including tetracycline operator elements was inactivated by the repressor protein, and inducer addition successfully initiated target protein expression. This is the first report to demonstrate tetracycline-induction system with strict on/off switching in marine cyanobacteria, and it should be useful for future bioenergy production.