Protective role of antioxidative enzymes and antioxidants against iron-induced oxidative stress in the cyanobacterium Anabaena sphaerica isolated from iron rich paddy field of Chhattisgarh, India

Abstract

Iron, as an essential element for plants and microorganisms, plays a significant role in photosynthesis, photopigment synthesis, nitrogen fixation, nucleic acid synthesis, etc. However, in iron rich environments, it causes stress by affecting various physiological activities including ROS generation and detoxification machineries. Here, we investigated the protective role of antioxidative enzymes and antioxidants against iron-induced oxidative stress in the cyanobacteria, <em>Anabaena sphaerica</em> from the iron rich regions of Chhattisgarh. We evaluated various morpho-physiological modifications at different concentrations of iron (0, 20, 50, 75 and 100 &micro;M FeCl₃). Microscopic and physiological characterization showed highest order of structural deformities, reactive oxygen species (ROS) generation and lipid peroxidation at 100 &micro;M FeCl₃ but growth was reduced only by 28%. Possibly, maximum superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities along with highest level of antioxidants (carotenoid, proline, cysteine and non protein thiol) played a major role in protecting the growth. As compared to 20 &micro;M FeCl₃ treated cells of <em>A. sphaerica</em>, almost equal growth and no structural alterations at 50 and 75 &micro;M FeCl₃may be correlated with minimum ROS, electrolyte leakage and malondialdehyde (MDA) content along with an activation of efficient ROS detoxification machinery i.e. enhanced level of antioxidative enzymes and antioxidants. Thus, the inherited property of <em>A. sphaerica</em> to grow at iron enriched condition make it more efficient microbe for improvement of the nitrogen status in the soil.