N2 Fixation by non-heterocystous cyanobacteria

Many, though not all, non-heterocystous cyanobacteria can fix N 2 .However, very few strains can fix N 2 aerobically.Nevertheless, these organisms may make a substantial contribution to the global nitrogen cycle.In this general review, N 2 fixation by laboratory cultures and natural populations of non-heterocystous cyanobacteria is considered.The properties and subcellular location of nitrogenase in these organisms is described, as is the response of N 2 fixation to environmental factors such as fixed nitrogen, O 2 and the pattern of illumination.The integration of N 2 fixation with other aspects of cell metabolism (in particular photosynthesis) is also discussed.Similarities and differences between different individual strains of nonheterocystous cyanobacteria are highlighted.