REGULATION OF NITROGEN-FIXATION IN HETEROCYST-FORMING CYANOBACTERIA

Some cyanobacteria are able to reduce atmospheric dinitrogen to ammoni a - a process where oxygen evolved by photosynthetic activity in the s ame cell is detrimental to nitrogen fixation. Strategies to avoid oxyg en range from temporal separation of nitrogen fixation and oxygen evol ution tin unicellular and filamentous, non-heterocystous strains) to s patial separation and cellular differentiation into nitrogen fixing he terocysts tin filamentous cyanobacteria). Recent research has begun to clarify the genes involved in nitrogen fixation, the mechanisms that regulate the expression of proteins involved in the assimilation of ni trogen from different sources and the way in which the cell is able to sense its nitrogen status.