CRYSTALLINE BACTERIAL-CELL SURFACE-LAYERS

Crystalline arrays of proteinaceous subunits forming surface layers (S -layers) are one of the most commonly observed prokaryotic cell envelo pe structures. They are ubiquitous amongst Gram-positive and Gram-nega tive archaeobacteria and eubacteria and, if present, account for the m ajor protein species produced by the cells. S-layers can provide organ isms with a selection advantage by providing various functions includi ng protective coats, molecular sieves, ion traps and structures involv ed in cell surface interactions. S-layers were identified as contribut ing to virulence when present as a structural component of pathogens. In Gram-negative archaeobacteria they are involved in determining cell shape and cell division. The crystalline arrays reveal a broad-applic ation potential in biotechnology, vaccine development and molecular na notechnology.