Cadmium removal from aqueous solution by gene-modified Escherichia coli JM109

The article extended the study on the bioaccumulation of cadmium by genetically engineered bacterium Escherichia coli (namely M4) simultaneously expressing a cadmium transport system and metallothionein (MT). The growth of M4 showed resistance to the presence of cadmium. Compared with Cd2+ uptake capacity by original host bacterial cells, The Cd2+ accumulation of M4 was enhanced more than one-fold. M4 could effectively bind Cd2+ over a range of pH from 4 to 8. The presence of Ni2+ and Mn2+ did not influence Cd2+ uptake remarkably, but Cu2+, Pb2+ and Zn2+ posed serious adverse effects. EDTA could drastically decrease Cd2+ bioaccumulation by M4, whereas the effect of citrate was relatively slight.