ABSTRACT

The outer membrane of the gram-negative bacterial cell wall is an asymmetrical distribution of various lipids interspersedwith proteins. Themembrane is “asymmetrical” in that the outer layer has an inner and outer leaf made up of different constituents. The outer layer contains almost all of the lipopolysaccharide (LPS) and the inner leaf contains phospholipids (PL) and no LPS. The outer face is highly charged and interactive with cations; so much so that the anionic groups can bind the fine-grained minerals in natural environments (1). LPS contains more charge per unit of surface area than any other phospholipid and is anionic at neutral physiological pH due to exposed ionizable phosphoryl and carboxyl groups (1). The biochemical pathways for the biosynthesis of each part of the LPS molecule have been deciphered (2). The biosynthesis of O-antigen, lipid A, and the core polysaccharide region are independent, arising from different genes and transported to the outermembrane separately by a partially characterized mechanism (2,3).