Antagonistic activity of bioactive compounds extracted from cyanobacterium Oscillatoria isolated from oil refinery waste

The aim of the present study was to isolate cyanobacteria from oil refinery waste water and detection of antagonistic activity of their extracts on four species of pathogenic bacteria. The cyanobacterium was isolated and purified on Blue green algae medium number ۱۱ (BG-۱۱) medium. Methanol and water extracts prepared from the cultured cyanobacterium after ۴۵ days growth on BG-۱۱ medium. The bioactive antagonistic effect of extracts was investigated on Escherichia coli (PTCC ۱۳۹۹), Pseudomonas aeruginosa (PTCC ۱۷۰۷), Bacillus cereus (PTCC ۱۰۱۵) and Staphylococcus aureus (PTCC ۱۱۱۲) via well diffusion method. The chemical composition of the effective extracts was detected by gas chromatography Mass spectrometry (GC-MS). The isolated bacterium detected as Oscillatoria based on microscopic morphological characteristics. The methanol extract of the cyanobacterium showed considerable antagonistic effect on Gram-negative bacterial species (growth inhibition zone of ۲۲.۳۳±۰.۴ mm for Escherichia coli (PTCC ۱۳۹۹), and ۱۸.۶±۱.۵۲ mm for Pseudomonas aeruginosa, (PTCC ۱۷۰۷); while little effect on Gram-positive bacterial species (growth inhibition zone of ۹.۳±۰.۵۷ mm for Bacillu scereus (PTCC ۱۰۱۵) and ۷.۹±۰.۳ mm Staphylococcus aureus (PTCC ۱۱۱۲). The water extract of the cyanobacterium had no antagonistic effect on all experimented bacterial species. The chemical composition of the methanol extract detected as: ۲۸.۱۱% Dodecamethyl-cyclohexasiloxane, ۲۵.۷۶% Hexasiloxane, ۳.۷۵% Tetracosamethyl-cyclododecasiloxane (three related compounds) and ۳.۹۱% Bisabolol oxide A (unrelated compound). Minimal nutritional and environmental requirement, are advantages which set cyanobacteria as suitable candidates for production of antiviral, anti-tumor and antibacterial bioactive materials.