Effect of copper on nitrogen metabolism in free and immobilized cells of nostoc calcicola

The Nitrogenase and Glutamine synthetase activities were investigated in free living and immobilized cells of Nostoc calcicola under copper stress conditions. The maximum Cu concentration in free and immobilized N. calcicola cells was 60µM at which the immobilized cells were characterized by faster rate of nitrogenase activity than free cells. Immobilization was also associated with increase in glutamine synthetase, suggesting that the immobilized cells maintain sufficient ATP pool to drive energy expensive process of nitrogen metabolism. Both the enzymes in immobilized cells were less sensitive to Cu and degree of inhibition was less marked as compared to the free living cells. The tolerance of immobilized cells in terms of all the activities studied over free cells concluded that immobilized cells are more resistant to Cu in respect to nitrogen metabolism and it can be used as an effective biofertilizer.