Toxicity and Uptake of Nickel+2 by Synechocystis sp. Isolates

Abstract

The uptake of heavy metal ions by microorganisms may present an alternative method for their removal from wastewater. In this study, 10 cyanobacteria were isolated from Kucukcekmece Lagoon (Turkey). All the cyanobacterial isolates were examined for Nickel(II) concentrations in the range of 5-25 mg/L. EC₅₀ values of the isolates were determined by probit analysis. Synechocystis sp. BASO403 (EC₅₀ of 17.41 mg/L) and Synechocystis sp. BASO404 (EC₅₀ of 2.56 mg/L) were selected from among the isolates based on their capacity to produce extracellular polysaccharides (EPS) which were 143 mg/L and 44 mg/L, respectively, for bioaccumulation at 15 mg/L Ni(II) concentration. The BASO404 isolate displayed a higher Ni(II) accumulation (95%), especially on the cell surface than BASO403 (51%) after a 7-day incubation period. A reverse relationship between EPS capacity and Nickel bioaccumulation (p<0.01) was indicated, but a positive correlation was observed between EPS capacity and Nickel toxicity (p<0.01). It is suggested that EPS from two isolates of Synechocystis sp. plays a protective role for Ni(II) toxicity