Beta-lactam in a heteroatomic ring structure, consisting of three 
carbon atoms and one 
nitrogen atom (Fig. 1). The beta-lactam ring is part of several 
antibiotics, such as 
penicillin, which are therefore also called 
beta-lactam antibiotics. These antibiotics work by inhibiting the bacterial 
cell wall synthesis. This has a lethal effect on 
bacteria, especially on 
Gram-positive ones. Bacteria can become 
resistant against beta-lactam antibiotics by expressing 
beta-lactamase.
  
Figure 1: Penicillin-G. Beta-lactam ring marked blue.
 
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