Effect of Sodium Deficiency on Mixotrophic Cultures of Anabaena variabilis

Response to NaCl of nitrate assimilation and nitrogenase activity of the cyanobacterium Anabaena sp. PCC 7120 and its mutants

“…Nitrogenase activity which was at a residual level in Na ¦ -starved cells, increased almost 11fold after the addition of 500 mmol l −1 NaCl in the nutrient solution, indicating a role for Na ¦ as a nitrogenase activator. The requirement for Na ¦ of N 2 -fixation has been observed in Anabaena variabilis (Nieva et al 1990), Anabaena torulosa Fernandes et al 1993), Anabaena cylindrica (Brownell and Nicholas 1967) and Nostoc muscorum (Fernández Valiente et al 1984). Na ¦ -deficiency-induced reduction in nutrient transport such as phosphate (Apte and Thomas 1985;Nieva et al 1990), ultimately limiting ATP supply, inorganic carbon (Kaplan et al 1984;Apte et al 1987) and metabolic alterations (Fernández Valiente et al 1988;Fig.…”

“…PCC 7942 (Rodríguez et al 1994) and Anabaena doliolum (Rai and Abraham 1995). Na ¦ deficiency affects anion transporters, namely HCO 3 − , NO 3 − and PO 4 3− (Nieva et al 1990). When NO 3 − and Na ¦ are present simultaneously, NO 3 − probably interacts with the Na ¦ carrier and inhibits Na ¦ influx competitively (Reddy et al 1989).…”

The gene sll0273 of the cyanobacterium Synechocystis sp. strain PCC6803 encodes a protein essential for growth at low Na+/K+ ratios

“…Despite the dependence on Na + , uptake of these nutrients does not seem to be driven by a sodium‐motive force, but rather are primarily ATP‐driven processes as deduced from bioenergetic analyses ( Ritchie, Trautman & Larkum 1997) and molecular approaches ( Omata 1995; Kaneko et al 1996 ). Further symptoms of sodium deficiency such as loss of nitrogenase activity ( Apte & Alahari 1994), chlorosis, and photo‐oxidative death of cells ( Nieva et al 1990 ) have been explained as secondary effects of reduced nutrient uptake. In illuminated cells of Synechocystis Na + was also shown to function directly in photosynthetic electron transport at the O 2 ‐evolving complex ( Zhao & Brand 1988).…”