Mohamed A Hefnawy, Mohamed I Ali and Salah Abdul-Ghany
Keywords: S. chartarum, lipid composition, membrane fluidity, copper and cobalt stress.
Abstract: The growth of S. chartarum markedly decreased with elevated concentrations of Cu and Co in the growth medium. Total lipids and proteins in isolated plasma membrane were increased at 400mg Cu or Col-1 and decreased above this concentration while, carbohydrates markedly increased with elevated concentrations of both metals. The total amount of detected phospholipids in the membranes was decreased at 800mg l-1 of both metal ions. However, Phosphatidyl ethanolamine and phosphatidyl glycerol showed an increase at this concentration. Moreover, most of the detected fatty acids (C16:0, C16:1, C18:1 and C18:2) in the plasma membrane were increased with elevated concentrations of both metals to approximately 1.5-2 fold higher than in the control except C16:1 at 800mg Cu l-1 highly increased to 24.9 times higher than in the control. Whereas, C16:0 was the only fatty acid which decreased at 800mg Col-1. The unsaturation index of fatty acids at 400mg l-1 exhibited a slight decrease while, at this concentration the fluorescence polarization value of DPH in the plasma membranes markedly increased. On the other hand, at 800mgl-1 the unsaturation index was increased while, fluorescence polarization value of DPH markedly decreased. This refers that the membrane at 400mgl-1 might be less fluid and at 800mgl-1 more fluid and cannot able to control the entry of toxic metals.
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