ANTIMICROBIAL ACTIVITIES OF FRESHWATER CYANOBACTERIUM, NOSTOC SP. FROM TAMDIL WETLAND OF MIZORAM, INDIA: AN IDENTIFICATION OF BIOACTIVE COMPOUNDS BY GC-MS

A freshwater microalga, Nostoc sp. isolated from Tamdil Wetland of Mizoram was tested for its algicidal, antibacterial and antifungal activity. Extracts were prepared with methanol, ethanol:water and dichloromethane:isopropanol and tested for their antimicrobial activity against nine microorganisms comprising of three chlorophycean algae (Chlorella vulgaris, Scenedesmus quadricauda and Selenastrum capricornatum), one cyanobacterium (Anabaena variabilis), three bacterial strains (Bacillus subtilis, Bacillus pumilus and Escherichia coli) and two fungal strains (Fusarium udum and Fusarium culmorum). Among the three extracts tested the methanol extract was found most effective on algal test organisms. The highest (60%) inhibitory effect was observed against A. variabilis by methanol extract followed by 31% inhibition by dichloromethane:isopropanol. When tested on bacterial strains, the highest inhibition zone (23.67±1.58mm) was observed in B. subtilis by dichloromethane:isopropanol extract followed by ethanol:water extract. In case of fungal activity, the highest inhibition zone (11.00±0.58mm) was observed in F. culmorum by dichloromethane:isopropanol extract and the rest of the extracts showed almost similar effect. MICs of each extract on all the organisms varied. The extracts were further analysed by UV-VIS Spectrophotometer, which reveals the presence of active compounds. Among the three extracts, methanol indicated the highest percentage inhibition and also obtained highest absorption spectra. So, this extract was analysed by GC-MS and we identified the presence of main components in the extract as 1,2-Benzenedicarboxylic acid, mono (2-ethylhexyl) ester, Phytol, n-Hexadecanoic acid, 9,12-Octadecadienoic acid, etc. Further study for purification of the potent compound will explain their usefulness in pharmaceutical and biotechnological industry.