Gram-negative bacteria are surrounded by two membrane bilayers separated by a space termed the periplasm. The periplasm is a multipurpose compartment separate from the cytoplasm whose distinct reducing environment allows more efficient and diverse mechanisms of protein oxidation, folding, and quality control. The periplasm also contains structural elements and important environmental sensing modules, and it allows complex nanomachines to span the cell envelope. Recent work indicates that the size or intermembrane distance of the periplasm is controlled by periplasmic lipoproteins that anchor the outer membrane to the periplasmic peptidoglycan polymer. This periplasm intermembrane distance is critical for sensing outer membrane damage and dictates length of the flagellar periplasmic rotor, which controls motility. These exciting results resolve longstanding debates about whether the periplasmic distance has a biological function and raise the possibility that the mechanisms for maintenance of periplasmic size could be exploited for antibiotic development.

革兰氏阴性细菌被被称为周质的空间隔开的两个膜双层包围。周质是与细胞质分开的多用途区室，其独特的还原环境允许蛋白质氧化，折叠和质量控制的机制更加有效和多样化。周质还包含结构元素和重要的环境传感模块，并允许复杂的纳米机器跨越细胞包膜。最近的工作表明，周质的大小或膜间距离是由周质脂蛋白控制的，周质脂蛋白将外膜锚定在周质肽聚糖聚合物上。该周质间膜距离对于感测外膜损伤至关重要，并决定了鞭毛周质转子的长度，该长度控制了运动性。