Bioaccumulation of heavy metals by fimbrial designer adhesins.

Naturally occurring adhesins bind to specific molecular targets in a lock-and-key fashion due to the composition of the binding domain of the adhesin. By introduction of random peptide libraries in a suitable surface exposed carrier protein it is possible to create and select designer adhesins with novel binding affinities. Type 1 fimbriae are surface organelles of Escherichia coli which mediate D-mannose sensitive binding to different host surfaces through the FimH adhesin, an integral part of these organelles. We have studied the ability of the FimH adhesin to display random peptide sequences. By serial selection and enrichment procedures specific sequences were identified which conferred the ability on recombinant cells to adhere to various metal oxides (PbO2, CoO, MnO2, Cr2O3). The properties inherent in these sequences permitted the distinct recognition of metals to varying degrees, indicating that this system allow for the isolation of peptide sequences with a variety of binding avidities. These studies demonstrate the potential and versatility of the FimH display system for presenting random peptide sequences. In addition, the possibility exists for the construction of microorganisms for the bioaccumulation of heavy metals from the environment.