The video discusses the structure and function of peptidoglycan, a component of bacterial cell walls, and its role in protecting bacteria. It highlights the historical discovery of penicillin during World War One and its impact on treating bacterial infections. The video explains the mechanism by which penicillin inhibits the enzyme transpeptidase, preventing the cross-linking of peptidoglycan chains, thereby weakening bacterial cell walls and making bacteria more vulnerable to external threats.

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