Bacterial lipopolysaccharide (LPS)

Molecular Classification

Other (cell envelope component), Glycolipid, Amphipathic molecule

Other Names

Lipopolysaccharide, Endotoxin, Bacterial outer membrane lipopolysaccharide, Gram-negative outer membrane lipopolysaccharide

Disease Roles

Infection (key to virulence of Gram-negative bacteria)Inflammation (induces strong immune and endotoxic shock)Sepsis (major trigger in septic shock)

Bacterial lipopolysaccharide Overview

Bacterial lipopolysaccharide (LPS) is a complex, amphipathic glycolipid and the primary structural component of the outer leaflet of the outer membrane of Gram-negative bacteria[1][5][7]. Composed of lipid A, a core oligosaccharide, and the highly variable O-antigen, LPS is essential for bacterial viability, outer membrane integrity, and serves as a major barrier to antibiotics and toxins[3][5][9]. LPS is also a potent stimulator of the host immune response; its lipid A portion is recognized by the innate immune system, leading to robust inflammatory reactions and, in high concentrations, endotoxic shock[3][5]. Due to its central biological roles, LPS and its biosynthesis/transport machinery (notably enzymes such as LpxA, LpxC, LpxD, LpxH, and the multi-protein Lpt transporter complex) are increasingly targeted by novel antibiotic strategies, and several experimental and approved drugs exploit LPS as either a direct target (polymyxins, experimental enzyme inhibitors) or a vulnerability[1][4][6][8][10]. The search for antibiotics that specifically impede LPS biosynthesis or integration has intensified due to its contribution to multidrug resistance and the urgent need for effective treatments against Gram-negative pathogens[1][2][4][8].

Mechanism of Action

Disruption of LPS biosynthesis (LpxA, LpxC, LpxD, LpxH inhibitors block pathway); Inhibition of LPS transport (blockade of Lpt transporter, e.g., LptD); Direct binding/disruption of outer membrane (polymyxins bind to LPS and disrupt membrane integrity)

Biological Functions

Structural integrity of Gram-negative bacterial outer membrane

Permeability barrier against hydrophobic and large molecules

Immune modulation (potent stimulator of immune response)

Antigenic determinant (O-antigen defines serotype)

Disease Associations

Infection (key to virulence of Gram-negative bacteria)

Inflammation (induces strong immune and endotoxic shock)

Sepsis (major trigger in septic shock)

Safety Considerations

Rapid LPS release upon bactericidal therapy may trigger endotoxic shock/sepsis
Cardiotoxicity and inflammatory side effects with LPS pathway inhibitors (e.g., LpxC inhibitors such as AchN-975)[8]

Interacting Drugs

Colistin[6]

Polymyxin B[6]

LpxA/LpxC/LpxD/LpxH inhibitors (experimental)[8][4]

POL7080 (LptD inhibitor)[4]

Peptide RJPXD33 (experimental; LpxA/LpxD inhibitor)[2]

AchN-975 (LpxC inhibitor, discontinued)[8]

Associated Biomarkers

Biomarker
Elevated circulating LPS (marker for Gram-negative bacteremia/sepsis)
Anti-LPS antibodies (serologic marker)