Physiological and biochemical characteristics of a copper tolerant and a wild type strain of Anabaena doliolum under copper stress

Abstract

Copper tolerance in Anabaena doliolum has been studied by comparing the physiological properties of its wild type and Cu-tolerant strains. A concentration dependent reduction in growth, pigments, protein, sugar, lipid and ATP content, photosynthetic electron transport chain, O₂-evolution, carbon fixation, nutrient uptake (NH⁺⁴ and NO^-_-3), nitrate reductase, nitrogenase, glutamine synthetase and alkaline phosphatase activities was noticed in both the strains following Cu-supplementation. The reduction in all parameters was higher in wild type than the tolerant strain. The latter produced a larger (19.5 %) lipid fraction than the wild type even in the absence of added metal. As compared to the wild strain, the tolerant strain showed enhanced enzyme activities, especially of alkaline phosphatase (20 % higher), low copper uptake and insignificant loss of K⁺ and Na⁺. The data on lipid production, loss of K⁺ and Na⁺, and uptake of copper collectively indicate a change in the permeability of the plasma membrane and a possible operation of <<exclusion mechanism>> in the tolerant strain thereby reducing the toxic effect of copper even at a high concentration.