Abstract:
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
