The main objective of this study was to test the antimicrobial activity of various solvent extracts (Aqueous, Chloroform, Ethyl acetate, Hexane and Methanol) of cyanobacterium, Cylindrospermum majus (Kutzing ex Born. et Flah.) against four pathogenic bacteria, in which two are Gram-positive Bacillus subtilis (MTCC-1427), Staphylococcus aureus (MTCC-1430) and two are Gram-negative Escherichia coli (MTCC-1302), Klebsiella pneumoniae (MTCC-4030) and four fungal pathogens of Aspergillus fumigatus (MTCC-4163), Aspergillus niger (MTCC-4325), Mucor sp. (MTCC- 3340) and Trichophyton mentagrophytes (MTCC-8476). The cyanobacterial strain C. majus was collected from the soil samples of paddy fields of Warangal district, India, and maintained in (BG-11 N-) medium. Antimicrobial activity was determined by agar disc diffusion method, in which the culture extracts of C. majus was exhibited with potential activity against bacterial and fungal growth by expressing various zone of inhibitions. The present results indicates that the culture crude extract of C. majus was shown with significant antibacterial activity (17.33 mm) in the solvent of Chloroform against K. pneumoniae and in fungal activity the Aqueous extract showed maximum inhibition zone (15.33 mm) against A. fumigatus under observation. Thus, the genus Cylindrospermum majus proved to be more potential in the bioassay studies against selected bacteria and fungi.
