Surface display of PbrR on Escherichia coli and evaluation of the bioavailability of lead associated with engineered cells in mice

Human exposure to lead mainly occurs by ingestion of contaminated food, water and soil. Blocking lead uptake in the gastrointestinal tract is a novel prevention strategy. Whole-cell biosorbent for lead was constructed with PbrR genetically engineered on the cell surface of Escherichia coli (E. coli), a predominant strain among intestinal microflora, using lipoprotein (Lpp)-OmpA as the anchoring protein. In vitro, the PbrR displayed cells had an enhanced ability for immobilizing toxic lead(II) ions from the external media at both acidic and neutral pH, and exhibited a higher specific adsorption for lead compared to other physiological two valence metal ions. In vivo, the persistence of recombinant E. coli in the murine intestinal tract and the integrity of surface displayed PbrR were confirmed. In addition, oral administration of surface-engineered E. coli was safe in mice, in which the concentrations of physiological metal ions in blood were not affected. More importantly, lead associated with PbrR-displayed E. coli was demonstrated to be less bioavailable in the experimental mouse model with exposure to oral lead. This is reflected by significantly lower blood and femur lead concentrations in PbrR-displayed E. coli groups compared to the control. These results open up the possibility for the removal of toxic metal ions in vivo using engineered microorganisms as adsorbents.