Investigating antimicrobial effects using Stochastic Optical Reconstruction Microscopy (STORM)*

The increasing antibiotic resistance of Gram-negative bacteria raises challenges to global health, resulting in an urgency of developing innovative treatments methods. One underexplored area is the host's innate immune response, which produces antimicrobial activity by histones and antimicrobial peptides (AMPs). While histones are primarily known for their role in condensing chromosomes, they are also found extracellularly in human blood during bacterial infections and tissue damage. However, the specific mechanism of antimicrobial activity due to histones remains unclear. Here, we investigated the cooperative behavior of histone and AMPs against bacterial infections using super-resolution microscopy. We observed that histone facilitates the localization of AMPs on cell membranes and AMPs increases the cytoplasmic uptake of histone, indicating a synergistic bactericidal effect of histone and AMPs. Our use of super-resolution stochastic optical reconstruction microscopy (STORM) showed that the number of histone and AMP molecules localizing on the cell was also synergistic, suggesting that histones enhanced the bacteria uptake of AMPs. This work sheds light on the multifunctional roles of histones and provides a potential framework to address antibiotic resistance.