Response of tolerant and wild type strains of Chlorella vulgaris to copper with special references to copper uptake system

Copper tolerance in Chlorella vulgaris has been studied by comparing physiological properties and copper uptake in a wild type strain and a copper tolerant one. A concentration dependent reduction in growth rate, dry mass, and content of chlorophyll a, protein, sugars and amino acids was noticed in both strains at 1.0 and 400 !g l 1 copper. The reduction in all parameters was higher in the wild type strain than in the tolerant one. As compared to the wild strain, the tolerant strain showed insignificant loss of potassium and sodium. The data on proline accumulation showed a positive relationship between copper toxicity and proline accumulation in both strains, more pronounced in the tolerant strain. The copper uptake was influenced by the copper concentrations the algae had been exposed to during their previous growth: the lower the copper concentration in the culture medium, the higher the activity of the uptake and the capacity of the cells to accumulate copper.