Interactions of nickel, lead and calcium on growth criteria and metabolic aspects in Phormidium fragile

ABSTRACT

The individual and interactive effects of calcium, nickel and lead were studied in Phormidium fragile grown in nutrient solutions supplemented with these metals, singly or in combination. Results showed that the cyanobacterium is more sensitive to nickel toxicity than to lead, whereas calcium stimulated dry weight gain. Calcium or lead alleviated the toxic effects of nickel. Addition of lead to calcium-containing media counteracted the stimulatory effects of calcium on growth of the alga. Chlorophyll a or carotenoid content was not significantly changed by all treatments except in case of Ca + Pb and Ni + Pb where chlorophyll a was significantly decreased. In the meantime, calcium seemed with a minor effect on the nitrogen components. Lead dramatically lowered total nitrogen whereas nickel had no effect on total nitrogen, increased protein content on the expense of other soluble nitrogen. All lead combinations favored high accumulation of ammonia, amino and peptide with a steep drop in the soluble nitrogen and slight increase in protein nitrogen. Nickel retained its stimulatory effect on protein accumulation in all its combinations. Results also revealed that all elements and their combinations insignificantly affected the phosphorus components, GOT, MDH, acid phosphatase, stimulated alkaline phosphatase and dramatically inhibited GPT and nitrate reductase. Calcium remarkably stimulated GPT