Which of the following is the primary target of methicillin in bacterial cells?

• A. RNA polymerase
• B. Penicillin-binding proteins (PBPs)
• C. DNA gyrase
• D. Ribosomal 30S subunit

Answer: (B)

Verified step by step guidance

1. Understand that methicillin is a type of β-lactam antibiotic, which primarily targets bacterial cell wall synthesis.
2. Recall that β-lactam antibiotics inhibit enzymes involved in the final stages of peptidoglycan cross-linking, which are essential for bacterial cell wall integrity.
3. Identify that the enzymes targeted by methicillin are called Penicillin-binding proteins (PBPs), which catalyze the cross-linking of the peptidoglycan layer.
4. Recognize that other options like RNA polymerase, DNA gyrase, and the ribosomal 30S subunit are targets of different classes of antibiotics (e.g., rifampin targets RNA polymerase, fluoroquinolones target DNA gyrase, and aminoglycosides target the 30S ribosomal subunit).
5. Conclude that the primary target of methicillin is Penicillin-binding proteins (PBPs) because inhibiting these proteins disrupts cell wall synthesis, leading to bacterial cell death.