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Isolation and identification of UV absorbing compounds from cynobacteria (Synechocystis) of District Mardan

. Sufaid khan, Anwar Hussain, Hamza Bacha, Nizar Nawaz, Majid Khan and Fawad Ali


Abstract

Blue green algae (also known as cyanobacteria) are photosynthetic prokaryotes found in a verity of environments. They may be aquatic, epiphytic, rhizosoheric, endophytic, found in fresh water or salty water or on damp soil. Biotechnological applications of cyanobacteria are many including their use as a source of UV absorbing pigments. During current study, Oscillatoria, Synechocystis, Gloeocapsa, Nostoc, Cyanothece and Microcystis were isolated from different locations of gujar garhi using a modified version of BG11. The strains were identified by colony morphology and light microscopy. The isolates were grown in the presence of tube light and sunlight and screened for UV absorbing compounds. Though all the strains produced UV absorbing compounds but only negligible or no absorbance in the UV-A and UV-B regions was recorded. Being the most harmful component of UV light due to their ability to reach the earth atmosphere, our aim was to induce production of compounds in the isolated cyanobacteria which can screen these components of UV radiation. Exposure to UV light was an excellent force inducing the isolates to produce UV-A and UV-B absorbing compounds. All the isolates produced significant quantities of phenols and flavonoids in both sunlight and tube light. However, Synechocystis, Gloeocapsa and Oscillatoria produces higher quantities of flavonoids than Cyanothece, Nostoc, and Microcystis. Production of phenols and flavonoids is greatly induced upon exposure of the isolated cyanobacteria to UV. Phenols and flavonoids are important for their role in the antioxidant system of cyanobacteria. Additionally, the also absorb significantly in the UV-A and UV-B regions as HPLC fractions containing phenols or flavonoids were efficient in absorbing in these regions. It may be concluded that cyanobacterial isolates naturally produce UV-C absorbing compounds, however UV-B and UV-A absorbing compounds induced by UV light exposure. Absorbance in these region is positively correlated with the production of phenols and flavonoids which are induced by exposure to UV light.

 

Index Terms- (Cyanobacteria, Synechocystis, UV absorbing compounds, UV Radiations, HPLC)

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