The properties of Escherichia coli cells, acquired by cell surface presentation of one or two hexa-histidine (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 Ni²⁺-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.