Nickel bioaccumulation by a marine bacterium Brevibacterium sp. (X6) isolated from Shenzhen Bay, China

Nickel bioaccumulation capacity of a marine Brevibacterium sp., designated as X6, was evaluated to explore its potential application in the bioremediation of Ni²⁺ pollutants in marine environments. The minimum Ni²⁺ inhibitory concentration and maximum Ni²⁺ bioaccumulation of X6 were 1000 mg/L and 100.95 mg/g, respectively, higher than most reported strains. Among the co-existing metal ions in seawater, K⁺ caused a slight adverse impact on Ni²⁺ uptake, followed by Na⁺ and Ca²⁺, whereas Mg²⁺ drastically inhibited Ni²⁺ bioaccumulation. Other heavy metals such as Co²⁺, Zn²⁺ and Cd²⁺ moderately affected Ni²⁺ binding, but the adverse effect of Cu²⁺ was severe. The investigation of the mechanism of Ni²⁺ bioaccumulation revealed that 66.34% of the accumulated Ni²⁺ was bound to the cell surface. Carboxylic, hydroxyl, amino and thiol groups participated in Ni²⁺ binding, while carboxylic group contributed the most, while thiol group may be more involved in Ni²⁺ binding at low Ni²⁺ concentrations.