Bacterial membrane phospholipids and lipopolysaccharide (LPS)

Bacterial membrane phospholipids and lipopolysaccharides (LPS) are essential structural elements of the bacterial cell envelope that maintain cellular integrity and provide a selective permeability barrier (Nature Reviews Microbiology, 2015). LPS, often referred to as endotoxin, is a complex glycolipid uniquely found in the outer leaflet of the outer membrane of Gram-negative bacteria, consisting of a conserved Lipid A moiety, a core oligosaccharide, and a variable O-antigen (NCBI Bookshelf, 2023). Phospholipids such as phosphatidylglycerol and phosphatidylethanolamine are found in both Gram-positive and Gram-negative membranes and are vital for maintaining the electrochemical gradient necessary for ATP synthesis and transport. These components are primary therapeutic targets for several classes of antibiotics, including polymyxins and lipopeptides, which disrupt the physical structure of the membrane to induce rapid bacterial killing. Beyond their structural role, LPS is a potent trigger for the host innate immune system through the Toll-like receptor 4 (TLR4) pathway. The massive release of LPS during severe infections or following antibiotic-induced bacterial lysis can lead to life-threatening inflammatory responses, such as sepsis and septic shock (PubMed, 2021).

Other names

EndotoxinLipid ABacterial outer membrane lipidsBacterial cell envelope lipidsBacterial membrane lipids

Drugs targeting these components typically act through physical disruption of the bacterial envelope. Polymyxins bind to the Lipid A portion of lipopolysaccharides (LPS) via electrostatic interactions with negatively charged phosphate groups, displacing divalent cations (Ca2+ and Mg2+) that stabilize the outer membrane, which leads to membrane permeabilization and cell death (StatPearls, 2023). Daptomycin inserts into the cytoplasmic membrane of Gram-positive bacteria in a calcium-dependent manner, specifically interacting with phosphatidylglycerol to cause rapid depolarization and loss of membrane potential (Journal of Biological Chemistry, 2016). Other agents, such as murepavadin, target the transport machinery (LptD) that moves LPS from the inner membrane to the outer membrane leaflet (Nature, 2014).