The cyanobacteria of Synechocystis sp. strain PCC 6803 and Anabaena sp. strain PCC 7120 are important models in basic and applied studies.Both species are conventionally cultured in BG11,although they show very distinct physiology.The effects of several nutrients in BG11 medium on the growth of Anabaena sp. strain PCC 7120 and Synechocystis sp. strain PCC 6803 were investigated.Results showed that the growth of Synechocystis sp. strain PCC 6803 and Anabaena sp. strain PCC 7120 was best at 10 mmol/L NO-3 and 2 mmol/L NO-3,respectively.Different concentrations of KHCO3 and NaHCO3 had different effects on the growth,indicating that both metal ions and HCO3- had a major role.For Na2S2O3  and Fe,the growth of Anabaena sp. strain PCC 7120 and Synechocystis sp. strain PCC 6803 was best at 10 mmol/L and 10 μmol/L,respectively.