标题： 接触诱导的大肠杆菌模型脂质膜分子重排 显示英文标题

标题： Contact-induced molecular reorganization in E. coli model lipid membranes

摘要： 生物膜是复杂的动态结构，对于细胞区室化、信号传导和机械完整性至关重要。真核膜的分子组织已被广泛研究，包括脂筏介导的横向组织和特定分子相互作用的影响。细菌膜传统上被认为在组成上更简单且结构均匀。然而，最近的证据表明，它们具有显著的脂质多样性，并可以形成类似于真核脂筏的功能微区，尽管缺乏固醇和鞘脂。然而，非特异性物理接触对原核膜局部分子组织和演化的影响力仍知之甚少。在此，我们使用一种模拟大肠杆菌内膜组成的模型脂膜，研究接触基底对膜纳米尺度演化的影响，当接近其相变温度$T_m$时。如预期的那样，基底的存在使$T_m$降低了$\sim$10{\deg }C，并诱导了双层的差异相变。然而，它同时使相变动力学减慢了近两个数量级，同时还实现了类似旋节线的横向分子重组。这导致了膜相的局部变化，出现了机械上更坚硬但仍然流体的纳米结构域，在依赖于基底的时间尺度上演化，与基底偏倚的脂质翻转机制一致。结果验证了之前的理论预测，并表明一种通用的物理机制——由膜-表面相互作用驱动——可以自发地在细菌膜中诱导脂质结构域的形成。这对其功能和机械作用将产生显著影响，包括在渗透压调节等过程中。 显示英文摘要

摘要： Biological membranes are complex, dynamic structures essential for cellular compartmentalization, signaling, and mechanical integrity. The molecular organization of eukaryotic membranes has been extensively studied, including the lipid raft-mediated lateral organization and the influence of the specific molecular interactions. Bacterial membranes were traditionally viewed as compositionally simpler and structurally uniform. Recent evidence, however, reveals that they possess significant lipid diversity and can form functional microdomains reminiscent of eukaryotic lipid rafts, despite lacking sterols and sphingolipids. Yet, the impact of unspecific physical contacts on the local molecular organization and evolution of the prokaryotic membranes remains poorly understood. Here we use a model lipid membrane mimicking the composition of Escherichia coli's inner membrane to investigate the impact of contacting substrates on the membrane nanoscale evolution, when close to its transition temperature, $T_m$. As expected, the presence of a substrate lowers the $T_m$ by $\sim$10 {\deg}C and induces a differential leaflet transition. However, it also slows down the phase transition kinetics by almost 2 orders of magnitude while simultaneously enabling a spinodal-like lateral molecular reorganization. This creates local alterations of the phase of the membrane, with the emergence of mechanically stiffer, yet still fluid nanodomains evolving over substrate-dependent timescales, consistent with a substrate-biased lipid flip-flop mechanism. The results verify previous theoretical predictions and demonstrate that a general physical mechanism -- driven by membrane-surface interactions -- can spontaneously induce lipid domain formation in bacterial membranes. This is bound to have notable consequences for its function and mechanical role, including in processes like osmotic pressure regulation.