Enhanced metalloadsorption of bacterial cells displaying poly-His peptides.

The properties of Escherichia coli cells, acquired by cell surface presentation of one or two hexahistidine (His) clusters carried by the outer membrane LamB protein, have been examined. Strains producing LamB hybrids with the His chains accumulated greater than 11-fold more Cd2+ than E. coli cells expressing the protein without the His insert. Furthermore, the hexa-His chains on the cell surface caused cells to adhere reversibly to a Ni(2+)-containing solid matrix in a metal-dependent fashion. Thus, expression of poly-His peptides enables bacteria to act as a metalloaffinity adsorbent. These results open up the possibility for biosorption of heavy ions using engineered microorganisms.