Compartmentalisation of nitrogenase in a non-heterocystous cyanobacterium:Trichodesmium contortum

In Trichodesmium contortum, nitrogenase was detected in only a limited number (about 10%) of microscopically distinguishable, consecutively arranged cells in central regions of the trichomes.Cells with nitrogenase also contained the photosystem II associated pigment phycoerythrin.These cells were not distinguishable from other cells on a structural basis, but were dearly visible at low magnification microscopy as all cells in the zone were more compact and shorter than those on either side.The compartmentalisation of nitrogenase into a chain of cells and in a possibly photosynthetic environment represents a previously undescribed phenomenon.The nitrogenase containing cells apparently perform the 0 2 protective function of heterocysts yet are different in several aspects.