The marine bacteria strains Si, S2 and S3, were isolated on seawater culturing medium containing Hg2+, Cd2+, Cr6+ or Ni2+ at concentrations of 20 mg L-1 and more. The isolates showed tolerance to these heavy metals. Si grew in the presence of 120 mg L-1 of Hg2+ and accumulated Hg2+ at pH 4-10. For the effect of co-existing cations on bioaccumulation of target metal, it was found that the effect depended on not only the variety and initial concentration of co-existing ions, but also the initial concentration of target metal and biomass dosage. A new parameter, the ratio of remaining bioaccumulation capacity (RRBC) of biomass, was therefore defined to evaluate such effect. Furthermore, the mechanism evaluation revealed that Si bound about 70% Hg2+ on the cell surface, and carboxyl group played an important role in Hg2+ binding. (C) 2012 Elsevier Ltd. All rights reserved.