Gram-negative bacterial outer membrane lipopolysaccharide (LPS) (LPS)

Lipopolysaccharide (LPS), also known as endotoxin, is the primary structural component of the outer leaflet of the Gram-negative bacterial outer membrane (Raetz & Whitfield, 2002). It consists of a hydrophobic lipid A anchor, a core oligosaccharide, and a distal O-antigen polysaccharide. LPS is essential for bacterial viability, providing a robust permeability barrier that protects the cell from toxic compounds, including many antibiotics and host-derived antimicrobial peptides (Sperandeo et al., 2019). From a clinical perspective, lipid A is a potent pathogen-associated molecular pattern (PAMP) that is recognized by the human TLR4/MD-2 receptor complex, triggering a massive pro-inflammatory cytokine release that can lead to sepsis and septic shock (Singer et al., 2016). Therapeutic targeting of this molecule involves polymyxin antibiotics, which bind to the negatively charged phosphate groups of lipid A to disrupt membrane integrity, or newer agents that inhibit the Lpt protein machinery responsible for transporting LPS to the cell surface (May & Silhavy, 2017). These interactions lead to increased membrane permeability and eventual cell death, making LPS a critical target in the fight against multi-drug resistant Gram-negative pathogens.

Other names

Lipid AEndotoxinLipoglycanBacterial outer membrane phospholipidsLPS

Drugs targeting this component typically act through two primary mechanisms. Cationic peptides like polymyxins bind to the negatively charged lipid A moiety of LPS, displacing divalent cations and physically disrupting the outer membrane's integrity (StatPearls, 2023). Alternatively, novel small molecules and macrocycles inhibit the lipopolysaccharide transport (Lpt) pathway, specifically the LptD/E translocon, which prevents the delivery of LPS to the cell surface and results in a compromised bacterial envelope (Sperandeo et al., 2019).