The biosorption of the toxic metal (nickel) from aqueous solutions on dried vegetative cell and spore-crystal mixture of Bacillus thuringiensis var. thuringiensis was tested under laboratory conditions as a function of pH, initial metal ion concentration and temperature. The characteristics of the adsorption process were investigated using Scatchard analysis. Scatchard analysis of the equilibrium binding data for metal ions on vegetative cell and spore-crystal mixture of B. thuringiensis gave rise to a linear plot, indicating that the Langmuir model could be applied successfully. Adsorption behaviour of nickel(H) ion on B. thuringiensis is expressed by both Langmuir and Freundlich isotherms. The adsorption data with respect to the metal provided an excellent fit to both isotherms. Ni(II) ion uptake of B. thuringiensis's spore-crystal mixture at 250 mg l(-1) was 15.7%, whereas its vegetative cell metal uptake was 10%. The best temperature for ion uptake was found to be at 35 degrees C. (C) 2007 Elsevier B.V. All rights reserved.