Visit the Ethics and Professionalism Course Web Site . The cyanobacteria are photosynthetic procaryotes that carry out an oxygen-evolving photosynthesis virtually identical to that of higher plants.
Some cyanobacteria are also capable of nitrogen fixation.
Because the enzyme that performs nitrogen fixation is extremely sensitive to oxygen, nitrogen fixation must occur in an anaerobic environment. Certain filamentous cyanobacteria such as Anabaena deal with this problem by physically separating the functions of nitrogen fixation and photosynthesis. Nitrogen starvation of Anabaena induces certain vegetative cells along the filament to develop into specialized cells called heterocysts. Heterocysts are the exclusive sites of nitrogen fixation within the filament and carry out an incomplete photosynthesis relative to neighboring vegetative cells. We are interested in how heterocyst development is regulated, in particular how gene expression is controlled during differentiation.