Influence of calcium on cadmium uptake and toxicity to the cyanobacterium Nostoc muscorum Meg 1

It is well known that Ca2+ interferes with uptake and expression of toxicity of Cd2+ in numerous organisms. This study demonstrated that the morphological alterations expressed in the cyanobacterium Nostoc muscorum Meg 1 cells exposed to 0.5 mg L−1 Cd2+ for 7 days were prevented when 10 mg L−1 Ca2+ was included in the experimental set-up. The spectroscopic analysis confirmed a severe reduction in contents of chlorophyll a, phycocyanin, allophycocyanin, phycoerythrin, carotenoids and total protein at the end of 168 h (7 days) in presence of Cd2+; inclusion of Ca2+ significantly lessened these effects. Heterocyst frequency, nitrogenase and, glutamine synthetase activities were similarly improved in the presence of Ca2+. Uptake studies showed a reduction in 94% biosorption of supplied Cd2+ to 50% in the presence of Ca2+ indicating its competition with Cd2+ binding onto the cyanobacterial cell surfaces.