Gram-negative bacterial outer membrane components (Lipopolysaccharide and Phospholipids) (LPS)

The Gram-negative bacterial outer membrane is a specialized asymmetric lipid bilayer that functions as a vital permeability barrier, shielding the bacterium from toxic substances and host immune defenses [6, 10]. Its outer leaflet is predominantly composed of lipopolysaccharides (LPS), while the inner leaflet consists of phospholipids [10, 13]. LPS is a complex glycolipid comprising lipid A, a core oligosaccharide, and an O-antigen; lipid A acts as a potent endotoxin that triggers the host's innate immune system via the Toll-like receptor 4 (TLR4) pathway [9, 12, 18]. Therapeutic agents such as polymyxins exploit the negative charge of LPS and phospholipids to bind and destabilize the membrane, causing lethal leakage of cellular components [1, 3, 4]. However, the clinical use of such drugs is often limited by significant safety concerns, including nephrotoxicity and neurotoxicity, as well as the risk of inducing severe inflammatory reactions like the Jarisch-Herxheimer reaction due to the rapid release of endotoxins during bacterial lysis [1, 4, 5].

Other names

EndotoxinLipid AGram-negative outer membraneBacterial cell envelope componentsLipopolysaccharide

Drugs targeting these components typically bind to the negatively charged lipid A portion of LPS and the phospholipids, displacing divalent cations (Mg2+ and Ca2+) that stabilize the membrane. This leads to increased membrane permeability, disruption of the bilayer structure, and leakage of intracellular contents, ultimately resulting in bacterial cell death [1, 3, 4].