Lipopolysaccharide of Gram-negative bacterium (LPS)

Lipopolysaccharide is a large glycolipid molecule that forms the major component of the outer leaflet of the outer membrane in Gram-negative bacteria such as *Escherichia coli*, *Salmonella*, *Shigella*, and others. It consists structurally of three main regions: 1. **Lipid A** – The hydrophobic anchor embedded in the bacterial membrane; it is highly conserved among species and responsible for most toxic biological activities. 2. **Core oligosaccharide** – An oligosaccharide chain attached directly to lipid A; less variable than other regions. 3. **O-antigen** – A long polysaccharide chain extending outward from the bacterium’s surface; highly variable between strains and responsible for antigenic diversity. LPS plays a critical role in maintaining bacterial structural integrity but is also recognized by host immune systems as a pathogen-associated molecular pattern via receptors such as Toll-like receptor 4. This recognition triggers potent innate immune responses—including fever, cytokine release, inflammation—and at high concentrations can lead to septic shock. Due to its central role in infection pathogenesis and host-pathogen interactions, LPS is considered both a virulence factor and an important therapeutic target—primarily through efforts aimed at neutralizing its toxic effects rather than inhibiting its biosynthesis directly.

Other names

EndotoxinBacterial lipopolysaccharideLPS of Gram-negative bacteria

Binding to lipid A region to disrupt membrane integrity and kill bacteria (e.g., polymyxins) Neutralization/blockade of endotoxin activity by antibodies or binding proteins Inhibition of Toll-like receptor 4 signaling pathway to reduce inflammatory response