Side chain: General structure of penicillin Ampicillin Be Cloxacillin CH Phenoxymethyl- Ticarcillin H B-lactam drugs β4 actam COoH B-lactamase(penicillinase) Peptide- glycan matrⅸ Penicillin-binding protein Rigid cell wall of Gram-positive bacteria 口β lactam drugs Lipopolysacch aride lay el Th in matrⅸ Penicillin-bindin g protein Gram-negative bacterial wall Fig 33-1 KMc5