Protective Role of Ca~(2+) towards Cu~(2+) Induced Toxicity on Photosynthetic Pigments, Morphology and Ultra-Structures of the Cyanobacterium Nostoc muscorum Meg 1

摘要

Ca~(2+) has been reported to play a protective role in many cyanobacteria against toxic effects of various metals. However there are very few reports of Ca~(2+) mediated protection in Cu~(2+) treated cyanobacterial cells. An initial study conducted toassess the influence of Ca~(2+) over Cu~(2+) induced effects on morphology, ultra-structure, photosynthetic pigments and total protein content of cyanobacterium Nostoc muscorum Meg 1 revealed that as little as 3 ppm Cuz+ can induce reduction in all these parameters by 50-80%. However when 10 ppm Ca~(2+)was present along with 3 ppm Cu~(2+), the Cu~(2+) 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 Ca~(2+). 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 Cu~(2+) treated cells whereas these effects were convincingly less in presence of Ca~(2+). Similarly decrease in protein concentration under the influence of Cu~(2+) was also positively modulated by the presence of Ca~(2+).