ABSTRACT
The outer membrane of Escherichia coli and most other gram-negative bacteria contains the endotoxin or lipopolysaccharide (LPS) molecule that is characteristic of these organisms. E. coli contains approximately 2 X 107 phospholipid molecules per cell, whereas each cell contains approximately 2 X 106 LPS molecules. Although important structural differences have been determined for the lipid A regions of various gram-negative bacteria, the structure of this region of LPS, like that of the core region, is relatively conserved. It is now well recognized that the lipid A region of LPS is responsible for the majority of the biological properties attributed to endotoxin. Accordingly, lipid A is critically involved in the pathophysiology of septic shock resulting from gram-negative bacteremia, and the morbidity and mortality resulting from sepsis and shock due to gram-negative bacteremia constitute an increasingly important medical problem.
