Enhanced bioadsorption of cadmium and nickel by E. coli displaying a metal binding motif using CS3 fimbriae.

Display of peptides on the surface of bacteria offers many new and exciting applications in biotechnology. Fimbriae is a good candidate for epitope display on the surface of bacteria. The potential of CS3 fimbriae of enterotoxigenic E. coli as a display system has been investigated. A novel cell surface display system with metal binding property was developed by using CS3 fimbriae. Short metal binding peptide, Gly-Cys- Gly-Cys-Pro- Cys- Gly- Cys- Gly as a cysteine rich peptide, was inserted into CS3 fimbriae and displayed on the surface of E. coli. Bacteria expressing hybrid pili with cysteine rich peptide could adsorb 392.5, 510 and 905 nmol of Ni2+, Cd2+ and Pb2+ per mg (dry weight) of cells, respectively, which are five-fold (nickel) and three-fold (cadmium) more than E. coli expressing native pili. Thus, expression of Cysrich peptide enables bacteria to act as a metalloaffinity adsorbent. These results open the possibility for biosorption of heavy metal ions using engineered microorganisms.