Final answer:
PBPs are essential for bacterial cell wall synthesis and are the targets of ß-lactam antibiotics, which can be rendered ineffective by genetic changes to PBPs or production of ß-lactamases, leading to antibiotic resistance.
Step-by-step explanation:
Penicillin-binding proteins (PBPs) play a critical role in the synthesis of bacterial cell walls by facilitating the crosslinking of the peptidoglycan layer. ß-lactam antibiotics, such as penicillin, mimic the structure of the peptidoglycan subunits, allowing them to bind irreversibly to PBPs and inhibit their activity. This action prevents the synthesis of a functional cell wall, leading to bacterial cell death. However, target modification is a common way for bacteria to develop resistance to these antibiotics. Mutations in the genes encoding PBPs can alter their structure so that ß-lactams can no longer bind effectively, rendering the drug ineffective against that strain of bacteria. For example, Staphylococcus aureus can acquire mecA, a gene encoding a PBP with low affinity for ß-lactams, leading to methicillin-resistant Staphylococcus aureus (MRSA). In other instances, the production of ß-lactamases, enzymes that break down ß-lactams, contribute to bacterial resistance. These strategies showcase the evolutionary arms race between antimicrobial drugs and bacterial defense mechanisms.