Antimicrobial peptides (AMPs) produced by multi-cellular organisms as their immune system’s defence against microbes are actively considered as natural alternatives to conventional antibiotics. Although substantial progress has been achieved in studying the AMPs, the microscopic mechanisms of their functioning remain not well understood. Here, we develop a new theoretical framework to investigate how the AMPs are able to efficiently neutralize bacteria. In our minimal theoretical model, the most relevant processes, AMPs entering into and the following inhibition of the single bacterial cell, are described stochastically. Using complementary master equations approaches, all relevant features of bacteria clearance dynamics by AMPs, such as the probability of inhibition and the mean times before the clearance, are explicitly evaluated. It is found that both processes, entering and inhibition, are equally important for the efficient functioning of AMPs. Our theoretical method naturally explains a wide spectrum of efficiencies of existing AMPs and their heterogeneity at the single-cell level. Theoretical calculations are also consistent with existing single-cell measurements. Thus, the presented theoretical approach clarifies some microscopic aspects of the action of AMPs on bacteria.

多细胞生物产生的抗菌肽（AMP）作为其免疫系统对微生物的防御，被积极认为是传统抗生素的天然替代品。尽管 AMP 的研究已取得实质性进展，但其功能的微观机制仍不清楚。在这里，我们开发了一个新的理论框架来研究 AMP 如何能够有效地中和细菌。在我们的最小理论模型中，随机描述了最相关的过程，即 AMP 进入单个细菌细胞以及随后对单个细菌细胞的抑制。使用互补主方程方法，明确评估 AMP 细菌清除动态的所有相关特征，例如抑制概率和清除前的平均时间。研究发现，进入和抑制这两个过程对于 AMP 的有效发挥同样重要。我们的理论方法自然地解释了现有 AMP 的广泛效率及其在单细胞水平上的异质性。理论计算也与现有的单细胞测量结果一致。因此，所提出的理论方法阐明了 AMP 对细菌作用的一些微观方面。