Lipopolisakaritte

Lipopolisakaritte is a term used in certain languages for lipopolysaccharide (LPS), a large molecule that is a major component of the outer membrane of most Gram-negative bacteria. LPS contributes to the structural integrity of the membrane and acts as a barrier to harmful substances.

The molecule has three main parts: lipid A, a hydrophobic anchor embedded in the membrane; a core polysaccharide; and the O antigen, a highly variable polysaccharide chain that extends outward from the cell surface. Lipid A is primarily responsible for much of the endotoxic activity, while the O antigen determines serotype and antigenic diversity across species.

Biological and medical significance: LPS is recognized by the host immune system via the Toll-like receptor 4 (TLR4) complex with MD-2, triggering inflammatory responses that can range from fever to septic shock in severe infections. LPS is heat-stable and is often used as a model endotoxin in research. It can be released in large amounts when Gram-negative bacteria are lysed by antibiotics, contributing to inflammatory symptoms.

Applications and notes: LPS is used in research to study innate immunity and signal transduction. Detoxified derivatives, such as monophosphoryl lipid A, are used as vaccine adjuvants. The molecule’s heterogeneity, especially in the O antigen, underlies extensive serotype diversity among Gram-negative species.