Abstract

ARUNAKUMARA, KKIU; XUECHENG, Z  and  SONG, X. Comparative study on bioaccumulation of lead and cadmium by the cyanobacterium Synechocystis sp. PCC 6803 under laboratory conditions. Cienc. mar [online]. 2007, vol.33, n.3, pp.271-280. ISSN 0185-3880.

Bioremoval techniques have been employed in cleaning water bodies that suffer from detrimental effects of heavy metal pollution. In the present laboratory study, bioaccumulation of Pb²+ and Cd²+ was assessed using the unicellular cyanobacterium Synechocystis sp. PCC 6803, a model organism widely used in genetic, physiological and morphological studies. Growth was measured as cell counts and showed that Pb²⁺, at low exposure concentrations (0.5 and 1 μg mL^-1), had a positive influence on Synechocystis sp. PCC 6803, resulting in slight growth stimulations; however, the species could not withstand long periods of exposure to both metals at higher concentrations (2, 4, 6 and 8 μg mL^-1). The highest inhibitions (53.14% and 70.07% for Pb²+ and Cd²+, respectively, at 8 μg mL^-1) were recorded after six days. Rapid metal removal was observed during the first two days of incubation, followed by a gradual reduction. Though the differences in accumulated amounts seemed to be narrow, the percentage of Pb²⁺ removed from the solution was always higher than that of Cd²⁺ in all the treatments. Accumulated amounts increased in a dose-dependent manner for both metals. The maximum accumulations (155.63 and 199.83 mg g^-1 dry weight for Pb²⁺ and Cd²⁺, respectively) were recorded at the end of six days. The species can be considered a good accumulator of metals, with high bioconcentration factor values of 20 657 and 24 980 for Pb²⁺ and Cd²⁺, respectively.

Keywords : Synechocystis sp. PCC 6803; growth; accumulated amount; bioconcentration factor.