Carneri Federico, Troiano Cassandra, Giaquinto Giuseppe, Roversi Daniela, Franzyk Henrik, Stella Lorenzo
Department of Chemical Science and Technologies, Tor Vergata University of Rome, 00133 Rome, Italy; Photoinduced Processes and Technologies Doctoral School, Department of Chemistry, Biology and Biotechnology, Perugia University, 06123 Perugia, Italy.
Department of Chemical Science and Technologies, Tor Vergata University of Rome, 00133 Rome, Italy.
J Colloid Interface Sci. 2025 Apr;683(Pt 1):1078-1086. doi: 10.1016/j.jcis.2024.12.099. Epub 2024 Dec 19.
The mutant selection window (MSW) is a range of antimicrobial concentrations, where some bacteria are killed, while others survive. Within this interval resistance may develop. Antimicrobial peptides (AMPs) are a promising class of antimicrobials that generally act by perturbing the integrity of bacterial membranes. Their MSW is typically narrower than that of traditional antibiotics, but it still encompasses about one order of magnitude of peptide concentrations. Phenotypic or genetic differences between individual cells may cause this heterogeneous bacterial response to AMPs. Therefore, we minimized the system complexity by investigating pore formation in liposomes with homogeneous size and composition. Surprisingly, the AMPs novicidin, P9-4, and Sub3 formed pores only in a fraction of vesicles, over a wide range of total peptide concentrations. By characterizing the water/membrane partition equilibrium of these three AMPs, we were able to report the vesicle-perturbing activity as a function of the membrane-bound peptide concentration. In this case, the curves became essentially step functions with well-defined (bound) concentration thresholds at which pores were formed in all liposomes. Therefore, the apparent heterogeneous effects of AMPs on vesicles were actually determined by variations in the fraction of membrane-bound peptides under different conditions, due to water-membrane partition. Unexpectedly, the thresholds coincided for all peptides in terms of bound amino acids per lipid (∼0.4), suggesting that the mechanism of pore formation primarily depends on the surface coverage by the AMPs.
突变选择窗（MSW）是一个抗菌浓度范围，在此范围内，一些细菌被杀死，而另一些细菌存活下来。在此区间内可能会产生耐药性。抗菌肽（AMPs）是一类很有前景的抗菌剂，通常通过破坏细菌膜的完整性发挥作用。它们的突变选择窗通常比传统抗生素的更窄，但仍涵盖大约一个数量级的肽浓度范围。单个细胞之间的表型或基因差异可能导致对AMPs的这种异质性细菌反应。因此，我们通过研究大小和组成均一的脂质体中的孔形成来最小化系统复杂性。令人惊讶的是，在很宽的总肽浓度范围内，AMPs新杀菌素、P9-4和Sub3仅在一部分囊泡中形成孔。通过表征这三种AMPs的水/膜分配平衡，我们能够将囊泡扰动活性报告为膜结合肽浓度的函数。在这种情况下，曲线基本上变成了具有明确（结合）浓度阈值的阶跃函数，在该阈值下所有脂质体中都形成了孔。因此，AMPs对囊泡的明显异质性效应实际上是由不同条件下膜结合肽比例的变化决定的，这是由于水-膜分配所致。出乎意料的是，就每个脂质的结合氨基酸而言（约0.4），所有肽的阈值是一致的，这表明孔形成机制主要取决于AMPs的表面覆盖率。
