Effect of ambient conditions on simultaneous growth and bioaccumulation of mercuric ion by genetically engineered E-coli JM109

Genetically engineered E. coli JM109, namely M1, which expressed both Hg2+ transport system and metallothionein, was tested for its capability of simultaneous growth and bioaccumulation of Hg2+ under low nutritional circumstances. The influential factors of ambient conditions, e.g. initial concentrations of mercuric ion, ionic strength, the presence of metal chelators and other coexisting metal ions were investigated. Hg2+ bioaccumulation behavior of M1 proved to be well coupled with its growth. NaCl was essential to the growth of M1. Of all tested NaCl concentrations, 0.04 mol/L was optimal. The presence of 0.1 mol/L CaCl2 or MgCl2 could promote the growth of M I and keep the Hg2+ removal ratio high, but the growth of M1 was inhibited seriously as the concentration of CaCl2 or MgCl2 reached 0.3 mol/L. Chelator EDTA had a significant influence on M1 growth and Hg2+ bioaccumulation, while the effect of citratio was little. The presence of other coexisting metal ions inhibited the growth of M1. The influential order was as follows: Cd2+ > Zn2+ > Cu2+ > Pb2+ > Ni2+. However, only Cd2+ and Cu2+ posed obviously adverse effects on Hg2+ bioaccumulation during the SG&B process. (c) 2006 Published by Elsevier B.V.