Abstract
Cyanobacterial taxa from extreme habitats represent a prolific source of antimicrobial agents. Cyanobacterial strain of Synechococcus elongatus Nageli 1849 (Chroococcales), isolated from hypersaline alkaline Lake of Wadi El Natrun, Egypt, was tested. Extraction of the lipophilic residue was performed using a modified approach of liquid/liquid extraction. The lipophilic residue was employed in antimicrobial bioassay on a wide range of pathogens comprising plant and human ones including bacterial and fungal strains. Antibacterial bioactivity of the cyanobacterium S. elongatus reached its maximum value after exposing the organism to 60 minutes of UV irradiation, while highest antifungal activity was observed when the inoculum was exposed to 5 minutes of UV irradiation. Gamma irradiation enhanced antibacterial bioactivity, exposure to the dose of 0.25 KGy was enough to support the highest antibacterial activity while the highest antifungal bioactivity was observed after exposure to 4 KGy. Conditions optimization for antimicrobial activities greatly enhanced both antibacterial and antifungal activities. Some of the adversely affected pathogens drug-resistant and showed wide host range such as Aspergillus niger. Therefore, the application of those bio-extracts could be effective in the biocontrol of those pathogens as this approach could be both cost-effective and applicable on a mass scale.