In the present study, ten (10) cyanobacterial strains isolated from Loktak Lake were examined for their possibility of increasing the content of extracellular ammonium excretion subjecting to various concentrations of nitrate and phosphate. The concentrations of nitrate and phosphate required for maximum growth varied with species.In the influence of nitrate, among heterocystous forms (Nostoc spp. BTA60, BTA61, BTA80,BTA67 and BTA950; Calothrix sp. BTA73; Anabaena sp. BTA964), maximum extracellular ammonium was excreted by Nostocmuscorum BTA950 (238.07 μgml-1) in 0N and minimum by Anabaena sp. BTA964 (25.95 μgml-1)in 2N. Among non-heterocystous forms (Phormidium spp. BTA52, BTA75 and BTA1048), maximum extracellular ammonium was excreted by Phormidium sp. BTA52 (134.09 μgml-1) in 1N and minimumby Phormidium sp. BTA1048 (55.91 μgml-1)in 0N. On the contrary, experiments on influence of phosphate, Nostocmuscorum BTA950 showed the maximum excretion of extracellular ammonium (233.79 μgml-1) in 1N and minimumby Anabaena sp. BTA964 (11.09 μgml-1) in 0N concentrations of phosphate. The findings indicate that these strains mayproved as promising microorganism for the extracellular ammonium excretion which could be exploited biotechnologically for the benefit of biofertilizer applications.
