6 Analysis of Lipopolysaccharides of Gram-Negative Bacteria

Publisher Summary This chapter discusses the analysis of lipopolysaccharides (LPS) of gram-negative bacteria. LPS are characteristic components of the cell wall of all Gram-negative bacteria and of at least some cyanobacteria. They are localized in the outer layer of the outer membrane, and are, in noncapsulated strains, exposed on the cell surface. They contribute to the integrity of the outer membrane and, as has been shown for enteric bacteria, protect the cell against the action of bile salts and (lipophilic) antibiotics. Isolated lipopolysaccharide, upon injection into higher organisms, exhibits a variety of biological (“endotoxic”) activities, such as the induction of fever, changes in the white blood cell count, diarrhoea, or even shock and death. Since the toxic activities are because of substances released from disintegrating bacteria, and not to an excreted exotoxin, lipopolysaccharide has been termed an endotoxin. Thus, the terms lipopolysaccharide, O-antigen, and endotoxin are used synonymously and describe either the chemical structure or discrete biological functions of the same substance.