Antimicrobial activity of some cyanobacteria

Abstract

Fifteen cyanobacteria belonging to Anabaena, Nostoc, Scytonema and Microcystis species isolated from various aquatic and terrestrial habitats were screened for antimicrobial activity. A disc diffusion assay was used to detect the antimicrobial activity of crude hydrophilic and lipophilic extracts as well as culture supernatants of cyanobacteria on solid agar medium. Methanolic extracts of Anabaena BT2, Nostoc Brf02, Nostoc Brf04 and Scytonema br1 at a concentration of 500 μg/disc showed prominent zone of inhibition against two Gram-negative bacteria (Pseudomonas sb1 and sb3). In liquid cultures addition of 500 μg/ml crude extracts produced 72-78 % growth inhibition of test bacteria. Out of all the cyanobacteria tested only the methanolic extract of Microcystis and chloroform fraction of Scytonema br1 showed significant anticyanobacterial activity against Anabaena BT2 and Nostoc pbr01 and antialgal activity against a green alga Bracteacoccus. In liquid cultures a concentration of 300 μg/ml of these extracts produced 73-85 % growth inhibition of the test organisms. None of the culture filtrates showed any antimicrobial activity.