Isolation of marine bacteria highly resistant to mercury and their bioaccumulation process

The marine bacteria strains S1, S2 and S3, were isolated on seawater culturing medium containing Hg(2+), Cd(2+), Cr(6+) or Ni(2+) at concentrations of 20 mg L(-1) and more. The isolates showed tolerance to these heavy metals. S1 grew in the presence of 120 mg L(-1) of Hg(2+) and accumulated Hg(2+) 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 S1 bound about 70% Hg(2+) on the cell surface, and carboxyl group played an important role in Hg(2+) binding.