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.