Topic overview

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Peptidoglycan is a cross-linked lattice of N-acetylglucosamine and N-acetylmuramic acid that gives bacteria shape and mechanical strength. Gram-positive bacteria have a thick peptidoglycan layer and teichoic acids; Gram-negative bacteria have thinner peptidoglycan, an outer membrane containing lipopolysaccharide, and a periplasmic space. These structures differ in how they interact with host defenses and antimicrobial agents. The lesson also introduces enzymes involved in wall synthesis and remodeling, including penicillin-binding proteins and autolysins, alongside antibiotic targets such as peptidoglycan synthesis. Special cases—including acid-fast bacteria and bacteria that lack or modify a conventional wall—show why cell-wall features matter for staining and treatment. Capsules are distinguished from the wall itself.