Properties and application perspectives of S-layer protein self-assembly

Nature develops different strategies to allow microorganisms to successfully interact with their environment, which encompasses diverse aspects such as nutrition, protection and communication. One strategy realized in case of bacteria and archaea is the formation of multilayered cell envelopes. The oldest known cell component of such multifunctional cell structures is the so-called surface layer (S-layer). S-layers are composed of proteins being able to self-assemble in highly regular layers forming oblique, square or hexagonal lattices on the surface of cells. These layers protect especially bacteria living in extreme habitats against diverse harmful environmental influences. In case of uranium mining waste pile isolates belonging to the genera Lysinibacillus and Bacillus it was proven that these S-layers act as scavenger for reactive oxygen species and as selective binding matrix for toxic elements and heavy metals. Based on these interesting natural functions and by combining S-layers with layer-by-layer techniques the development of various materials being interesting for an industrial application is possible. Thus, new metals selective filter materials, diverse nano-particular catalysts and sensor materials were successfully produced and tested for their applicability.