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 11 (bg-11) medium. methanol and water extracts prepared from the cultured cyanobacterium after 45 days growth on bg-11 medium. the bioactive antagonistic effect of extracts was investigated on escherichia coli (ptcc 1399), pseudomonas aeruginosa (ptcc 1707), bacillus cereus (ptcc 1015) and staphylococcus aureus (ptcc 1112) 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 22.33±0.4 mm for escherichia coli (ptcc 1399), and 18.6±1.52 mm for pseudomonas aeruginosa, (ptcc 1707); while little effect on gram-positive bacterial species (growth inhibition zone of 9.3±0.57 mm for bacillu scereus (ptcc 1015) and 7.9±0.3 mm staphylococcus aureus (ptcc 1112). the water extract of the cyanobacterium had no antagonistic effect on all experimented bacterial species. the chemical composition of the methanol extract detected as: 28.11% dodecamethyl-cyclohexasiloxane, 25.76% hexasiloxane, 3.75% tetracosamethyl-cyclododecasiloxane (three related compounds) and 3.91% 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.