This is a platform technology that enables the regulation of gene expression in cyanobacteria through the use of riboswitches. Synthetic riboswitches to precisely control gene expression and activated with an inexpensive commercially available compound have been constructed and tested in expression vector systems compatible with cyanobacteria. These riboswitches work through multiple mechanisms. Methods have also been developed to identify novel riboswitches that will function in cyanobacteria and respond to different ligands. Strains of cyanobacterial and other algae have been developed that exhibit resistance to predatory grazers. Methods for screening and selecting such strains are also included. The genetic basis of this resistance is the knock-out of a gene to prevent the expression a cell surface protein/antigen. Another advantage of the removal of this protein is that these mutants also exhibit the ability to auto-flocculate. The basis of this technology is a bioengineered cyanobacteria synthesizes a nutrient that is required by a specific targeted recipient organism in such a way that the nutrient is available only to that organism and not to a contaminating species. In the model system developed the nutrient provided is fixed nitrogen in a form most organisms cannot metabolize and the recipient organism has been engineered to metabolize that specific form of the compound. The underlying strategy of this technology should be applicable to other nutrients where the target organism can be engineered to utilize the provided form of the nutrient of interest. This technology utilizes engineered algae that express a protein(s) secreted into the growth medium which retards the settling of the cells in culture and that is safe and biodegradable. Such protein(s) can also be added exogenously to the culture medium. In addition it can also serve as a carrier to suspend other particles that are needed by the growing biomass. Keeping the cells suspended provides a more efficient cultivation process the light limiting effect on unsuspended cells has been mitigated and the need for mechanical agitation eliminated. Cells that remain in suspension can be less costly to harvest because less flocculation agent is required and the necessary flotation is achieved without having to employ a forth flotation step.
Cells that remain in suspension can be less costly to harvest because less flocculation agent is required and the necessary flotation is achieved without having to employ a forth flotation step.