Alterations in Antioxidative Defense System of Anabaena Variabilis in the Presence of Heavy Metals

A general increase in the level of heavy metals posses a pervasive threat to the natural ecosystem, although many heavy metals, when in trace amount are essential for various metabolic process in organism, they create physiological stress leading to generation of free radical, when in high concentration, stress in turn induces the production of reactive oxygen species. Cyanobacteria posses an effective stress combat system to cope with pressure by the help of cascade of antioxidants where superoxide dismutase act initially followed by catalase and peroxidases. The present study was conducted to evaluate the effects of heavy metal ions on the levels of antioxidant enzymes of the organism. Various effects of alkaline earth metal on cells were depicted by means of variations observed in cell size, shape and their density. The differential response of activities of all studied enzymatic antioxidants was investigated and it was observed that SOD activity showed was less in control and cobalt with passing time whereas in the presence of Mg2+, Mn2+,Cd2+,Hg2+,Zn2+ the activity was enhanced. CAT activity showed opposite pattern as CAT activity was significantly less in the presence of these metal ions as compared to SOD values, whereas SOD is correlated to the POD activity and the organism grown in Mn2+, Zn2+,Hg2+ showed similar pattern. This may help in developing a strategy to improve cyanobacterial tolerance towards these metals in order to develop strains so to be used to reclaim the environmental stress.