Original paper

Effect of exogenous supply of antioxidants on UV-B induced oxidative stress in a cyanobacterium Cylindrospermum sp.

Chris, Abhishek; Zeeshan, Mohd.; Abraham, Gerard


UV-B (0.2 Wm−2 for 15 and 60 min) exposure of the cyanobacterium Cylindrospermum sp. resulted in greater generation of hydrogen peroxide (H2O2), malondialdehyde (MDA) accumulation, electrolyte leakage and proline accumulation. However, cells pre-treated with proline (1mM) and ascorbate (0.1mM) showed considerable decrease in generation of H2O2, MDA accumulation and electrolyte leakage when exposed to UV-B. The activities of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD) were also decreased by the supplementation of proline. Supplementation of ascorbate led to reduced intracellular proline content which indicates that the increase in cellular proline is not a necessary consequence of stress in the presence of a free radical scavenger. These results strongly suggest that proline acts as a free radical detoxifying agent conferring tolerance to Cylindrospermum sp. to UV-B exposure and rule out the possibility of merely improving the antioxidant machinery of the cells as reported by us earlier.