Bacterial cell membrane phospholipids and lipopolysaccharides (LPS/PL)

Bacterial cell membrane phospholipids and lipopolysaccharides (LPS) are fundamental structural components of the bacterial cell envelope that maintain cellular integrity and act as a permeability barrier. Phospholipids, such as phosphatidylglycerol and phosphatidylethanolamine, form the primary lipid bilayer of the cytoplasmic membrane in both Gram-positive and Gram-negative bacteria (Muller et al., 2016). Lipopolysaccharides are unique to the outer membrane of Gram-negative bacteria and consist of a hydrophobic Lipid A anchor, a core oligosaccharide, and an O-antigen polysaccharide (Raetz & Whitfield, 2002). LPS is a potent endotoxin; its Lipid A component is recognized by the host's TLR4-MD2 complex, triggering a massive pro-inflammatory cytokine release that can lead to life-threatening sepsis and septic shock (Park & Lee, 2013). These lipid components serve as the primary targets for several 'last-resort' antibiotics, including polymyxins and lipopeptides. Polymyxins, such as colistin, bind to the Lipid A of LPS and phospholipids to disrupt the outer and inner membranes of Gram-negative pathogens (Zavascki et al., 2007). Daptomycin specifically targets anionic phospholipids in the cytoplasmic membrane of Gram-positive bacteria, causing rapid membrane depolarization and cell death (Muller et al., 2016). While effective against multi-drug resistant bacteria, targeting these structures requires careful management due to potential toxicities like nephrotoxicity and the risk of inflammatory surges during bacterial lysis.

Other names

EndotoxinLipid ABacterial membrane lipidsOuter membrane lipopolysaccharideCytoplasmic membrane phospholipidsBacterial cell envelope lipids

Drugs target these components by binding to the Lipid A moiety of lipopolysaccharides in Gram-negative bacteria or to anionic phospholipids like phosphatidylglycerol in Gram-positive bacteria, leading to membrane permeabilization, depolarization, and the leakage of essential intracellular contents (Zavascki et al., 2007; Muller et al., 2016).