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

摘要

Genetically engineered E. coli JM109, namely M1, which expressed both Hg~(2+) transport system and metallothionein, was tested for its capability of simultaneous growth and bioaccumulation of Hg~(2+) 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. Hg~(2+) 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 CaCl_2 or MgCl_2 could promote the growth of M1 and keep the Hg~(2+) removal ratio high, but the growth of M1 was inhibited seriously as the concentration of CaCl_2 or MgCl_2 reached 0.3 mol/L. Chelator EDTA had a significant influence on M1 growth and Hg~(2+) 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: Cd~(2+) > Zn~(2+) ≥ Cu~(2+) > Pb~(2+) > Ni~(2+). However, only Cd~(2+) and Cu~(2+) posed obviously adverse effects on Hg~(2+) bioaccumulation during the SG&B process.