Abstract

The present study evaluates the phytochemical screening and antimicrobial activity of two species of cyanobacteria  namely,  Phormidium  chalybeum  and  Leptolyngbya  tenuis  isolated  from  hospital discharge waste waters near Mangalore. They were maintained in BG11 media. In vitro screening of organic solvents (methanol, ethanol, chloroform and petroleum ether) and their aqueous extracts was carried out against seven species of bacteria namely, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Aeromonas hydrophila, Proteus vulgaris, Pseudomonas aeruginosa and Klebsiella pneumoniae. Antimicrobial assay was carried out using disc-diffusion method. All the four organic solvents and aqueous extracts of the species showed activity against tested bacteria. Methanol extract was highly effective against all the bacterial strains (p<0.01) except E.coli followed by ethanolic extract (p<0.05), while ethanolic extract showed significant minimum inhibitory concentration (MIC) values (p<0.01).  The  study  revealed  antifungal  activity  against  Aspergillus  niger,  Aspergillus  flavus  and Candida albicans whileAlternaria alternata was found to be resistant in the ethanol and water extracts, whereas the methanol and chloroform extracts exhibited significant inhibition activity (p<0.01), followed by diethyl ether extract (p<0.05). Methanolic extracts showed significant MIC values (p<0.01) against tested fungi. The occurrence of cyanobacteria in such waters may necessitate the development of certain adaptation strategies and production of antimicrobial compounds.

Key words: Cyanobacteria, pharmaceutical wastes, antimicrobial activity, minimum inhibitory concentration, pharmaceutical importance.