[Kdo2-lipid A modification in gram-negative bacteria--a review].

In most Gram-negative bacteria, the Kdo2-lipid A moiety of lipopolysaccharide forms the outer monolayer of the outer membrane. Diverse covalent modifications of Kdo2-lipid A may occur in bacteria to survive different environmental conditions. Kdo2-lipid A is usually synthesized on the cytoplasmic surface of the inner membrane. After the core oligosaccharide is attached to Kdo2-lipid A, the molecule is flipped to the outer surface of the inner membrane, where the O-antigen repeats are attached to form lipopolysaccharide. Kdo2-lipid A could activate the innate immune system through TLR4. Therefore, researches on the structure modification of Kdo2-lipid A would be useful for developing new vaccines and adjuvants.