Background & Objectives: Expansion of microbial drug resistance, have indicated to introduce new source of drugs with antimicrobial properties such as antimicrobial secondary metabolites which produced of Cyanobacteria spp. Antimicrobial activity of Cyanobacteria spp. of Urmia Lake catchment area was not already reported, therefore in this research, antibacterial and antifungal properties of cyanobacteria varieties isolated from this ecosystem and identification of the potent strains were investigated.

  Method: Different environmental samples screened for isolation of cyanobacterial strains. Cyanobacterial extracts were prepared by using different solvents. The effect of these extracts was evaluated by disc diffusion method and by measuring minimum inhibitory concentrations (MIC) against some gram positive and gram negative bacteria and fungi. Cyanobacteria spp. with the high antimicrobial activity was identified according to Microscopic and macroscopic characters and 16SrRNA sequences.

  Results: In this research, 54 cyanobacterial strains were isolated that six strains with significant antimicrobial activity identified as Gloeocapsa sp., Anabaena sp., Nodularia sp., Synechococcus sp., Leptolyngbya sp. and Chroococcus disperses. the highest antimicrobial activity achieved by the chloroform extract on gram positive bacteria and fungi. Minimum inhibitory concentration (MIC) levels for the cyanobacterial strains were ranged 20 to 80 µg/ml and Leptolyngbya sp. showed the highest effects on Candida krusei with MIC level 20 µg/ml.

  Conclusion: According to the results, cyanobacteria can be a source of production new antimicrobial compounds.the results showed that the filamentous cyanobacteria Anabaena sp., Nodularia sp., and Leptolyngbya sp. produce active compounds against gram positive bacteria and yeasts.