Relationship of combined nitrogen sources to salt tolerance in freshwater cyanobacterium Anabaena doliolum

Abstract

Higher concentrations of NaCl inhibit the growth and reduce the specific growth rate of the freshwater cyanobacterium Anabaena doliolum. Among the nitrogen sources tried, nitrate protected the cyanobacterial cells most from salt toxicity. However, supplementing of medium with nitrate could increase the adaptability of the cells at sublethal doses but it would not permit growth at otherwise lethal doses of 300 mmol 1‐1 NaCl. Nitrate uptake was proportionally related to the NaCl level in the medium. The uptake of sodium was minimum when nitrate was simultaneously available to the cells, indicating the interaction of nitrate with the Na+ carrier. Na+ efflux was maximum in N2, ammonia, urea and nitrate in decreasing order. This led to the conclusion that Na+ influx plays the critical role in salt tolerance, rather than its efflux.

Ultrastructure of the fresh water cyanobacterium Anabaena variabilis SPU 003 and its application for oxygen-free hydrogen production

“…Inorganic nitrogen sources signi¢cantly reduce hydrogen production. Cyanobacteria are known to use amino acids as nitrogen source and hence the acids may inhibit nitrogenase activity [14].…”

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

“…Nitrogenous compounds nitrate, ammonium and glutamine have been reported to enhance salt tolerance in cyanobacteria (Apte and Alahari 1994;Rai and Abraham 1995). Among these, nitrate is found to be more effective than ammonium (Reddy et al 1989;Rai and Abraham 1995;Rai and Tiwari 1999).…”

Ultrastructure of the fresh water cyanobacteriumAnabaena variabilisSPU 003 and its application for oxygen-free hydrogen production

“…Inorganic nitrogen sources significantly reduce hydrogen production. Cyanobacteria are known to use amino acids as nitrogen source and hence the acids may inhibit nitrogenase activity [14].…”