Bacitracin acts by inhibiting what part of the cell wall synthesis pathway?

• A. Inhibits cross-linking of NAM-NAM
• B. Inhibits the bactoprenol carrier cycle
• C. Disrupts cell membrane integrity
• D. Blockade of peptidoglycan precursor synthesis

Answer: (B)

Bacitracin blocks the recycling of the bactoprenol carrier, the lipid that ferries peptidoglycan subunits across the cytoplasmic membrane. By binding to the pyrophosphate form of bactoprenol and preventing its dephosphorylation, the carrier cannot be reused to move new cell-wall units outside the membrane, so cell wall synthesis stalls. This is different from blocking cross-linking of existing strands (that’s what transpeptidase inhibitors do), disrupting membrane integrity, or stopping the initial synthesis of peptidoglycan precursors in the cytoplasm.