Protective Role of Ca²⁺ Towards Cu²⁺ Induced Toxicity on Photosynthetic Pigments, Morphology and Ultra-Structures of the Cyanobacterium Nostoc Muscorum Meg 1

Rabbul Ibne A. Ahad, Balakyntiewshisha L. Kynshi and Mayashree B. Syiem

Department of Biochemistry, North-Eastern Hill University, Shillong – 793022, India.

Corresponding Author E-mail: mayashreesyiem@yahoo.co.in

DOI : http://dx.doi.org/10.13005/bbra/2665

ABSTRACT: Ca²⁺ has been reported to play a protective role in many cyanobacteria against toxic effects of various metals. However there are very few reports of Ca²⁺ mediated protection in Cu²⁺ treated cyanobacterial cells. An initial study conducted to assess the influence of Ca²⁺ over Cu²⁺ induced effects on morphology, ultra-structure, photosynthetic pigments and total protein content of cyanobacterial Nostoc muscorum Meg 1 revealed that as little as 3 ppm Cu²⁺ can induce reduction in all these parameters by 50-80%. However when 10 ppm Ca²⁺ was present along with 3 ppm Cu²⁺, the Cu²⁺ induced toxic effects were lessened by 55-85% within 7 days. Bright field and scanning electron microscopic study showed that morphological changes including broken filaments; rupture, elongation and shrivelling of cells were lessened upon inclusion of Ca²⁺. Ultra-structural studies conducted using transmission electron microscopy showed detachment of cell membrane from cell wall, shrinkage of cellular matter; compromised thylakoid membranes and increased number of polyphosphate bodies in the Cu²⁺ treated cells whereas these effects were convincingly less in presence of Ca²⁺. Similarly decrease in protein concentration under the influence of Cu²⁺ was also positively modulated by the presence of Ca²⁺.

KEYWORDS: Ca²⁺ Mediated Protection; Cu²⁺ Toxicity; Morphology; Nostoc Muscorum Meg 1; Photo-Pigments; Ultra-Structure

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