Adaptation to salt of the photosynthetic apparatus in cyanobacteria

Abstract

Cyanobacteria grow under a wide range of environmental conditions. Their distribution in environments of highly diversified osmotica is well documented [ 11. Hence, the photosynthetic apparatus must adapt to the different degrees of salinity in the habitat. This is achieved by means of either osmoregulation or on the level of the organism [2] or modification of the enzyme structure [3]. Here we correlated the salt tolerance of the whole organism with the salt tolerance of activities of the photosynthetic apparatus and NADPH-cytochrome c reductase in 4 cyanobacteria characterized by different degrees of salt tolerance: marine Spirulina tolerates up to 3-times sea water [4] ; Gzlothrix scopulorum, sea water [S]; Spirulina platensis, brackish water [6]; Nostoc muscorum 7119, fresh water. We show that the soluble components of the final steps of photosynthetic electron transport constitute a salt-sensitive site and that salt tolerance may be acquired during growth in saline water.