COMPARTMENTALIZATION OF NITROGENASE IN A NONHETEROCYSTOUS 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 nitroge nase also contained the photosystem II associated pigment phycoerythri n. These cells were not distinguishable from other cells on a structur al basis, but were clearly visible at low magnification microscopy as all cells in the zone were more compact and shorter than those on eith er 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 pe rform the O-2 protective function of heterocysts yet are different in several aspects.