Response of n(2)-fixing cyanobacteria to salt.

The effect of salt on photosynthetic activity, acetylene reduction, and related activities was examined in two species of cyanobacteria, Nostoc muscorum and Calothrix scopulorum. Photosynthesis was more resistant to high salt concentration than was N(2) fixation. The salt resistance of both activities increased after a period of exposure of the cells to salinity. The transfer of electrons via ferredoxin and ferredoxin-nicotinamide adenine dinucleotide phosphate reductase was found to be extremely sensitive to salt. In comparison, the transfer of reducing power by glucose-6-phosphate dehydrogenase, isocitric dehydrogenase, and photosystem 1 was less affected by NaCl, whereas glutamine synthetase exhibited higher tolerance to salt.