Bacterial death through large pore formation

Antimicrobial resistance is an increasing threat to global health but the development of new antibiotics has stalled. We explore antimicrobial mechanisms from the human immune system to identify new antimicrobial mechanisms. Histones and antimicrobial peptides (AMPs) are key components in innate immunity and have an important role in neutrophil extracellular traps and lipid droplets. Their antimicrobial effects are synergistic and contribute to bacterial clearing but the mechanism remains poorly understood. Here, we report a synergistic antimicrobial mechanism that arises between histones and AMPs against Gram-negative bacteria. Using stochastic optical reconstruction microscopy and total internal reflection fluorescence microscopy, we show that histones and AMP on bacteria at single-molecule precision. Our use of cryogenic electron microscopy (cryo-EM) we find that this combination forms large membrane pores. To elucidate the kinetics, we developed a mathematical model of pore formation across the four leaflets of the bacterial inner and outer membranes. Our findings indicate that the synergy arises from differential targeting of the membrane leaflets by histones and AMPs, providing insights into this immunity mechanism and suggesting new potential antimicrobial approaches against Gram-negative bacteria.