Bacterial cell wall and membrane permeability

The bacterial cell wall and membrane permeability refer collectively to the ability—or restriction—of molecules crossing the protective barriers surrounding bacteria. The primary structural component is the cell wall, mainly composed of peptidoglycan—a mesh-like polymer providing rigidity against osmotic pressure. In Gram-negative bacteria, an additional outer membrane contains lipopolysaccharide and embedded proteins called porins that regulate passive diffusion based on size, charge, flexibility, dipole moment—and are major determinants for antibiotic entry. Efflux pumps further restrict intracellular accumulation by actively exporting toxic compounds. Many antibiotics exploit these structures by either inhibiting their biosynthesis/cross-linking enzymes (β-lactams, glycopeptides) or directly disrupting their integrity (polymyxins, gramicidin), leading ultimately to increased permeability followed by loss of viability. However, bacteria can adapt through modifications in these barriers—altered porin expression/composition or changes in lipid A—that confer significant drug resistance phenotypes.

Other names

Bacterial envelope permeabilityCell envelope barrierCell wall permeabilityMembrane permeability (bacteria)

Drugs targeting this property act by one or more of the following mechanisms: - Inhibiting synthesis or cross-linking of peptidoglycan in the cell wall—leading to loss of structural integrity and lysis ([β-lactams], glycopeptides) - Disrupting membrane structure—increasing membrane permeability leading to leakage of cellular contents ([polymyxins], gramicidin) - Forming pores/channels that allow uncontrolled ion flux across membranes [gramicidin]