Bacterial outer membrane phospholipids and lipopolysaccharides (LPS)

The bacterial outer membrane is a specialized asymmetric lipid bilayer found in Gram-negative bacteria, characterized by an inner leaflet of phospholipids and an outer leaflet primarily composed of lipopolysaccharides (LPS). LPS, also known as endotoxin, is a complex glycolipid consisting of Lipid A, a core oligosaccharide, and an O-antigen polysaccharide, which provides structural integrity and acts as a selective permeability barrier against antibiotics and host immune factors (Raetz & Whitfield, 2002, Annual Review of Biochemistry). In the context of human disease, LPS is a potent pathogen-associated molecular pattern (PAMP) that triggers the innate immune system via the TLR4/MD-2 receptor complex, potentially leading to life-threatening sepsis and septic shock (Opal, 2010, Toxins). Therapeutic targeting of these components involves drugs like polymyxins, which bind directly to the Lipid A moiety to destabilize the membrane, or novel inhibitors that block the transport of LPS from the inner membrane to the cell surface (Sperandeo et al., 2019, BBA Molecular and Cell Biology of Lipids). While effective against multidrug-resistant pathogens, targeting the outer membrane often carries risks of nephrotoxicity and neurotoxicity due to the narrow therapeutic window of available agents (Velkov et al., 2013, Future Microbiology). Modern drug development also focuses on neutralizing circulating LPS to mitigate the inflammatory cascade associated with severe Gram-negative infections.

Other names

EndotoxinLipid AGram-negative outer membraneBacterial glycolipidsOuter membrane vesicle components

Disruption of the outer membrane through displacement of divalent cations (Mg2+ and Ca2+) from phosphate groups of Lipid A; inhibition of the lipopolysaccharide transport (Lpt) pathway; neutralization of circulating endotoxin to prevent TLR4 activation.