Nickel is a toxic heavy metal found in the environment as a result of various natural and industrial activities.Epidemiological studies have identified nickel as potentially carcinogenic and allergenic to humans. Bioreduction of nickel has not been documented however biosorption and bioaccumulation may be possible. Nickel tolerance in a preselected consortium was studied and found to be gradual. Aeration of preloaded consortium showed a rapid efflux of Ni(II). Uptake in Glucose minimal media was higher than the others tested. The accumulation of Nickel sulphate was higher than the other nickel salts tested. A cell density of 20% allowed greater accumulation of Ni(II) as demonstrated by Atomic absorption spectrophotometry. Uptake in whole cells was higher (65%) than immobilized cultures (48-51%). The optimum pH and temperature for nickel uptake with respect to this consortium was found to be 7.0 and 40oC respectively. The uptake with Nickel sulphate was found to be higher than other nickel salts tested. The uptake of nickel was reduced by over 78 % in distilled water and by 58% in phosphate buffer in presence of respiratory inhibitors like Sodium azide. Other metals such as Cu 2+ and Mg 2+ completely inhibited nickel uptake, while Zn2+ inhibited nickel uptake by 94.25% when compared to controls.
