Screening of antimicrobial and cytotoxic activities of two marine cyanobacteria collected from mangrove backwater at sandspit, pakistan

Two strains of cyanobacteria form backwaters mangrove forest were isolated and examined for potential antagonist activity against clinical and environmental strains of bacteria and yeast. The cyanobacterial fractions (from sea and distilled water, ethanol, sodium hydroxide) exhibited variable activity. Results from agar spot assay revealed that the ethanolic fraction of Phormidium breve and seawater extract of Aphanocapsa litoralis, exhibited positive antagonistic activity against Candida albicans. Most of bacterial strains were resistant to test extracts. The cytotoxicity test was employed using Artemia salina. The probit analysis (95% confidence interval) revealed that the bioassay was highly sensitive against Phormidium breve ethanolic extract and moderately sensitive against Aphanocapsa litoralis sea water fraction. The undiluted crude fractions of ethanolic and seawater were found to be lethal and effective. Median lethal concentration (LC50) values of Phormidium breve ethanolic extract was 0.02 mg/ml (20 ppm) and Aphanocapsa litoralis sea water fraction was found to be 6.2 mg/ml (6200 ppm) after 24-hours respectively. These findings indicate the fractions were biologically active and provide a baseline for further antifungal protein research of mangrove associated cyanobacterial strains. (author)