INVESTIGATING THE PHYSIOLOGICAL RESPONSES OF THREE ENDAPHIC STRAINS OF CYANOBACTERIA TO CRUDE OIL CONCENTRATIONS IN LIMITED SALINITY AND IRRADIATION CONDITIONS.

The objective of the present study is to investigate the physiological responses of three soil strains of cyanobacteria (collected from areas contaminated with oil in southern Iran and from paddyfields in north of Iran) to crude oil concentrations in limited salinity (NaCl) and irradiance conditions. Three cyanobacteria species of Fischerella sp. ISC107, Nostoc sp. ISC101, Phormidium sp. ISC108 were assayed. After purification, samples were grown in BG11 and BG110 media. The results showed that the efficiency of hydrocarbon source utilization of Phormidium sp. ISC108 was higher than in other cyanobacteria in crude oil treatment. The highest growth rate was observed at 3% crude oil concentration in Phormidium sp. ISC108. Also, the highest levels of allophycocyanin, phycocyanin, phycoerythrin, chlorophyll, carbohydrate, protein and phycobiliprotein were obtained from cyanobacteria Phormidium sp. ISC108 had larger phycobilisomes than the other strains (3.99 μg/gdw). The highest ratio of PSII/PSI was observed in Fischerella sp. ISC107. The highest levels of photosynthetic indices were assigned to 3% crude oil. In fact, reducing photosynthetic efficiency in higher levels of crude oil could be related to the toxic effect of organic hydrocarbons on algae growth. It can be concluded that the cyanobacteria can be used as a bioremediation for decomposing crude oil especially in the coastal area of the Persian Gulf and the Caspian Sea. The results of this research can be valuable for reducing the contamination which affects the fauna and flora of the marine ecosystems in Iran. [ABSTRACT FROM AUTHOR]