Surfactin, a cyclic lipoheptapeptide produced by Bacillus subtilis, is a surface-active antimicrobial that targets the barrier function of lipid membranes. It inserts itself into the membrane, where it forms conductive pores. Depending on its concentration, it eventually disintegrates the membrane in a detergent-like manner. The molecular details of this activity are not yet sufficiently understood, nor are the mechanisms that the surfactin producer employs to resist its own toxic product. We have previously shown that B. subtilis modifies its membrane lipid composition upon the onset of surfactin production, mainly increasing the cardiolipin content. Here we show that the increased cardiolipin content leads to a decreased surfactin-induced leakage of liposomes reconstituted from lipids isolated from the surfactin producer. This stabilizing effect of cardiolipin is concentration-dependent. Using a propidium iodide-based cell permeabilization assay, we further confirmed that the cytoplasmic membrane of the mutant B. subtilis strain lacking cardiolipin was substantially more susceptible to the action of surfactin, even though the amount of bound surfactin was the same as in the wild-type strain. We propose that membrane remodelling; due to the increase in cardiolipin content, contributes to the surfactin tolerance of B. subtilis.

Surfactin是枯草芽孢杆菌（Bacillus subtilis）产生的环状脂肽，是一种靶向脂质膜屏障功能的表面活性抗微生物剂。它插入膜中，在其中形成导电孔。取决于其浓度，它最终以类似洗涤剂的方式使膜崩解。这种活性的分子细节尚未得到足够的了解，表面活性素生产者用来抵抗其自身有毒产物的机理也尚未得到足够的了解。我们之前已经显示了枯草芽孢杆菌在产生表面活性素时改变其膜脂质组成，主要增加心磷脂含量。在这里，我们显示出增加的心磷脂含量导致表面活性素诱导的脂质体泄漏减少，该脂质体由从表面活性素生产者分离的脂质重构。心磷脂的这种稳定作用是浓度依赖性的。使用基于碘化丙啶的细胞通透性测定，我们进一步证实了缺乏心磷脂的枯草芽孢杆菌突变菌株的细胞质膜对表面活性素的作用更敏感，即使结合的表面活性素的量与野生环境中的相同。型菌株。我们建议进行膜重塑；由于心磷脂含量的增加，有助于表面活性素的耐受性枯草杆菌。