How Antimicrobial Peptides Kill Bacteria: It's Not Just About Making Holes

Antimicrobial peptides kill bacteria through more mechanisms than just punching holes in membranes. While three classic pore-forming models exist — 'barrel-stave,' 'carpet,' and 'toroidal-pore' — growing evidence shows that many peptides can also cross into bacterial cells and inhibit internal processes including cell wall synthesis, nucleic acid synthesis, protein synthesis, enzymatic activity, and membrane septum formation during cell division.

This is a comprehensive review published in Nature Reviews Microbiology examining the different models of how antimicrobial peptides form pores in bacterial membranes and how they kill microorganisms through intracellular mechanisms. The author synthesized evidence from structural, biophysical, and microbiological studies across invertebrate, plant, and animal species.

Understanding how antimicrobial peptides actually kill bacteria is essential for developing them as antibiotics. If peptides work through multiple mechanisms simultaneously — membrane disruption and internal target inhibition — bacteria would have a much harder time developing resistance, making these peptides particularly valuable in the age of antibiotic resistance.

This 2005 Nature Reviews paper was a paradigm shift in the antimicrobial peptide field. Before it, most researchers focused almost exclusively on membrane disruption. By highlighting intracellular targets, Brogden opened the door to designing synthetic peptides optimized for specific killing mechanisms — a research direction that has become central to developing peptide antibiotics against drug-resistant bacteria.

As a review article, no new experimental data was generated. Many of the pore-forming models were derived from artificial membrane systems that may not perfectly replicate living bacterial membranes. The relative importance of membrane disruption versus intracellular inhibition for any given peptide was not yet fully resolved at the time of publication.