ABSTRACT
Like other cell surface components of prokaryotic organisms, S-layers as metabolic expensive products must have evolved as a component of specific interactions between the cell and the environment. Both bacteria-(Fig. 14.1) and archaea-carrying S-layers are ubiquitous in the biosphere. Thus, it is now evident that the supramolecular concept of an “isoporous monomolecular (glycol)protein lattice” can provide organisms with an advantage of selection in quite diverse habitats. Although a considerable knowledge has accumulated on the structure, assembly, chemistry, and genetics of S-layers, relatively less firm data is available about their specific biological functions [5, 7-9]. It is now recognized that they can function as protective coats, molecular sieves, molecule and ion traps, promoters for cell adhesion and surface recognition, and virulence factors in pathogenic organisms. In those archaea that possess S-layers as the exclusive envelope component external to the cytoplasmic membrane, the lattices act as a framework that determines cell shape [10-12] and as a structure aiding in the cell division process (Table 14.1).
