Genetic engineering of Escherichia coli for enhanced uptake and bioaccumulation of mercury

Synthetic phytochelatins (ECs) are a new class of metal-binding peptides wi th a repetitive metal-binding motif, (Glu-Cys)(n)Gly, which were shown to b ind heavy metals more effectively than metallothioneins, However, the limit ed uptake across the cell membrane is often the rate-limiting factor for th e intracellular bioaccumulation of heavy metals by genetically engineered o rganisms expressing these metal-binding peptides. In this paper, two potent ial solutions were investigated to overcome this uptake limitation either b y coexpressing an Hg2+ transport system with (Glu-Cys)(20)Gly (EC20) or by directly expressing EC20 on the cell surface. Both approaches were equally effective in increasing the bioaccumulation of Hg2+. Since the available tr ansport systems are presently limited to only a few heavy metals, our resul ts suggest that bioaccumulation by bacterial sorbents with surface-expresse d metal-binding peptides may be useful as a universal strategy for the clea nup of heavy metal contamination.