Bacterial surface display surface display of metal-binding sites

Abstract

Biosorption of metal ions is a metabolism-independent metal uptake event at the cell wall polysaccharides, associated molecules, and functional groups. It involves mainly the ion-exchange, chemisorption, adsorption, and, in some cases, also the inorganic microprecipitation of certain heavy metal species. In the search for strategies allowing for enhancements of the biosorption capacity for a specific metal ion, display of particular amino acid sequences with the capacity to form coordination centers for the metal ions at the microbial cell wall has proved to be a promising approach. To anchor particular metal-binding moiety by means of recombinant DNA technology, a wide range of cell-surface display systems is available for both Gram-negative and Gram-positive bacteria. These involve outer membrane proteins, autotransporters, lipoproteins, cell-wall associated and covalently bound proteins, S-layer proteins and subunits of surface appendages. Surface displays of metal-binding oligopeptides, metallothioneins, or metalloproteins has been shown to improve the natural biosorption capacity or even selectivity for particular metal ion in model cells Escherichia coli. Furthemore, this approach was successfully extended to environmentally robust Pseudomonas, Cupravidus or Moraxella species. This chapter provides overview of available surface display systems and summarizes evidence supporting suitability of cell-surface-display technology in tailoring microbial biosorbents. © 2011 Springer Science+Business Media B.V.