The properties of Escherichia coli cells, acquired by cell surface pre
sentation of one or two hexahistidine (His) clusters carried by the ou
ter 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. Fur
thermore, the hexa-His chains on the cell surface caused cells to adhe
re reversibly to a Ni2+-containing solid matrix in a metal-dependent f
ashion. 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.