Bacterial outer membrane lipopolysaccharide (LPS)

Bacterial outer membrane lipopolysaccharide (LPS) is a large amphipathic glycolipid that forms the major component of the external leaflet of the outer membrane in virtually all Gram-negative bacteria. It consists structurally of three main regions: 1. Lipid A – The hydrophobic anchor embedded within the bacterial outer membrane; responsible for most toxic effects (“endotoxin” activity). 2. Core oligosaccharide – A short sugar chain attached directly to lipid A. 3. O-antigen polysaccharide – A highly variable repeating glycan polymer extending outward from the cell surface; determines antigenic specificity between strains. LPS plays essential roles in maintaining structural integrity and protecting bacteria from hostile environments, including antibiotics and host immune factors. In mammals, recognition by innate immune receptors—primarily Toll-like receptor 4—triggers robust inflammatory responses that are protective at low levels but can cause severe pathology such as septic shock when uncontrolled. Because it is essential for viability in most Gram-negative pathogens and central to their interaction with hosts, bacterial outer membrane lipopolysaccharide is considered both a key virulence factor and an important therapeutic target—especially for drug development aimed at disrupting its synthesis/transport or neutralizing its toxic effects during infection.[1][2][3][4][7]

Other names

LipopolysaccharideEndotoxinBacterial lipopolysaccharideGram-negative bacterial LPS

For drugs that interact with this molecule: Disruption of outer membrane integrity by binding to lipid A region, leading to increased permeability and cell death (e.g., polymyxins)[9] For host response modulation: Neutralization/blockade of endotoxin activity to prevent excessive immune activation/sepsis