Vol. 1, Issue 12, Part J (2015)

Abstract
Two Lead resistant cyanobacterial taxa, Lyngbya majuscula and Spirulina subsalsa isolated from Lead contaminated area, were exposed to sub-lethal dose of lead (5 mg L-1) for short and long term duration to understand the biochemical modulation in stress related compounds in metal exposure. Both the taxa showed gradual increase in Pb (II) accumulation with time (5-30 mg/g), where Spirulina showed 6 times more accumulation compared to that of Lyngbya. The growth in terms of chlorophyll content at this particular concentration remained almost unchanged in Lyngbya up to 7 days of exposure followed by growth suppression, but Spirulina showed no significant variation in metal exposure during the experimental tenure. The toxicity level, as indicated by total ROS content was determined in terms of malondialdehyde production and maximum value was obtained after long term exposure for both the strains. Upregulation with variation in stress enzyme activities like catalase, ascorbate peroxidase and super oxide dismutase along with proline level were observed within 1 to 24 h of metal exposure giving protection to the metal exposed cell against oxidative stress. But in long term exposure, high rate of carotene accumulation and reduction in cellular glutathione pool may provide protection to oxidative damage of metal treated cyanobacteria.