Microbial lipid bilayer and cellular membrane

Microbial lipid bilayers and cellular membranes serve as the fundamental physical barrier separating the internal environment of bacteria and fungi from their external surroundings (Nature Reviews Microbiology, 2017). These membranes are composed of a complex mixture of phospholipids, proteins, and specific sterols or hopanoids that maintain structural integrity and facilitate essential processes such as nutrient transport, signal transduction, and energy production via the proton motive force (UniProt). In pathogenic microbes, the membrane is a critical therapeutic target because its disruption leads to the rapid loss of intracellular contents, dissipation of electrochemical gradients, and eventual cell death (PubMed, 2021). Drugs like polymyxins and daptomycin specifically target bacterial membranes by binding to lipopolysaccharides or phosphatidylglycerol, respectively, while polyene antifungals like amphotericin B target ergosterol in fungal membranes (StatPearls, 2023). Despite their efficacy, targeting microbial membranes presents challenges in selectivity, as similarities between microbial and mammalian lipid compositions can lead to off-target toxicities, such as nephrotoxicity and neurotoxicity (NIH, 2022). Furthermore, the outer membrane of Gram-negative bacteria acts as an additional permeability barrier, necessitating specialized drugs that can penetrate or disrupt this layer to reach the inner membrane (Journal of Biological Chemistry, 2019). The evolution of resistance through membrane remodeling, such as the modification of lipid A or changes in sterol content, remains a significant hurdle in infectious disease management (Nature Communications, 2020).

Other names

Bacterial cell membraneFungal cell membraneCytoplasmic membraneMicrobial plasma membraneProkaryotic membraneBacterial inner membraneBacterial outer membrane

Drugs targeting microbial membranes typically act through physical disruption of the lipid bilayer, leading to pore formation, membrane depolarization, and the leakage of essential intracellular ions like potassium (K+). For instance, lipopeptides like daptomycin insert into the Gram-positive membrane in a calcium-dependent manner, causing rapid depolarization and cessation of DNA, RNA, and protein synthesis (StatPearls, 2023). Polymyxins act as detergents that bind to the lipid A component of lipopolysaccharides in Gram-negative bacteria, disrupting both the outer and inner membranes (Nature Reviews Microbiology, 2017). Polyene antifungals, such as amphotericin B, bind to ergosterol in fungal cell membranes, creating aqueous pores that cause lethal ion leakage and oxidative stress (PubMed, 2020). Additionally, some newer glycopeptides like telavancin exhibit a dual mechanism by inhibiting cell wall synthesis and simultaneously dissipating bacterial membrane potential (NIH, 2021).