Abstract:Abstract: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.