Bacterial cell envelope anionic phospholipids and lipopolysaccharides (LPS/APL)

Bacterial cell envelope anionic phospholipids and lipopolysaccharides are fundamental components that define the structural integrity and defensive capabilities of bacterial cells. Anionic phospholipids, including phosphatidylglycerol and cardiolipin, are essential for maintaining the cytoplasmic membrane's organization and the function of various membrane-bound proteins [17, 19]. Lipopolysaccharides (LPS) are the signature molecules of the Gram-negative outer membrane, forming a dense, negatively charged barrier that protects the bacterium from environmental stressors and many antibiotic classes [21, 24]. These lipids are critical therapeutic targets; for example, polymyxins exploit the negative charge of LPS to disrupt the outer membrane, while daptomycin targets anionic phospholipids to induce membrane depolarization in Gram-positive pathogens [2, 5]. Beyond their structural role, LPS is a potent endotoxin that triggers severe inflammatory responses in the host, often leading to life-threatening conditions such as sepsis and septic shock [23]. Consequently, agents that target these lipids or their biosynthetic and transport pathways represent vital tools in the treatment of multidrug-resistant bacterial infections [11, 13].

Other names

Bacterial cell envelope lipidsBacterial membrane phospholipidsLipopolysaccharide (LPS)Anionic phospholipidsEndotoxinLipid APhosphatidylglycerol (PG)Cardiolipin (CL)

Drugs targeting these components primarily act by disrupting the structural and functional integrity of the bacterial cell envelope. Cationic lipopeptides, such as polymyxins, bind electrostatically to the negatively charged lipid A component of lipopolysaccharides (LPS) in the outer membrane of Gram-negative bacteria, displacing stabilizing divalent cations (Ca2+ and Mg2+) and leading to membrane permeabilization [2, 8]. Daptomycin, in a calcium-dependent manner, interacts with anionic phospholipids like phosphatidylglycerol in the cytoplasmic membrane of Gram-positive bacteria, causing membrane depolarization, ion leakage, and rapid cell death [1, 5, 10]. Additionally, inhibitors of LPS biosynthesis (e.g., LpxC inhibitors) or transport (e.g., Lpt inhibitors) compromise the outer membrane barrier, increasing bacterial susceptibility to other antibiotics and host immune factors [11, 12].