The isolation of heterocystous and non-heterocystous cyanobacterial strains was carried out by dilution and pour plate method. The taxo-nomic identification was done following the keys given by Desikachary (1959) and Starmach (1966). The non-heterocystous isolates were maintained in nitrogen enriched (+N) and heterocystous isolates were maintained in nitrogen deficient (-N) medium in temperature regulated culture room under controlled light and dark cycles