Unit of Bacterial Genetics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland.
Int J Mol Sci. 2019 Jan 16;20(2):356. doi: 10.3390/ijms20020356.
Distinguishing feature of the outer membrane (OM) of Gram-negative bacteria is its asymmetry due to the presence of lipopolysaccharide (LPS) in the outer leaflet of the OM and phospholipids in the inner leaflet. Recent studies have revealed the existence of regulatory controls that ensure a balanced biosynthesis of LPS and phospholipids, both of which are essential for bacterial viability. LPS provides the essential permeability barrier function and act as a major virulence determinant. In , more than 100 genes are required for LPS synthesis, its assembly at inner leaflet of the inner membrane (IM), extraction from the IM, translocation to the OM, and in its structural alterations in response to various environmental and stress signals. Although LPS are highly heterogeneous, they share common structural elements defining their most conserved hydrophobic lipid A part to which a core polysaccharide is attached, which is further extended in smooth bacteria by -antigen. Defects or any imbalance in LPS biosynthesis cause major cellular defects, which elicit envelope responsive signal transduction controlled by RpoE sigma factor and two-component systems (TCS). RpoE regulon members and specific TCSs, including their non-coding arm, regulate incorporation of non-stoichiometric modifications of LPS, contributing to LPS heterogeneity and impacting antibiotic resistance.
革兰氏阴性细菌外膜（OM）的一个显著特征是其不对称性，这是由于 LPS（外膜小叶）和磷脂（内膜小叶）存在于 OM 的外小叶中。最近的研究揭示了存在调节控制，以确保 LPS 和磷脂的平衡生物合成，这两者对于细菌的生存能力都是必不可少的。LPS 提供必需的渗透屏障功能，并作为主要的毒力决定因素。在革兰氏阴性细菌中，有超过 100 个基因参与 LPS 的合成、在内膜（IM）的内小叶中的组装、从 IM 中的提取、向 OM 的转运以及对各种环境和应激信号的结构改变。尽管 LPS 高度异质，但它们共享定义其最保守疏水性脂质 A 部分的共同结构元素，该部分与核心多糖相连，在光滑细菌中进一步延伸为 O-抗原。LPS 生物合成的缺陷或任何失衡都会导致主要的细胞缺陷，从而引发由 RpoE sigma 因子和双组分系统（TCS）控制的包膜响应信号转导。RpoE 调节子成员和特定的 TCS，包括它们的非编码臂，调节 LPS 的非化学计量修饰的掺入，有助于 LPS 的异质性并影响抗生素耐药性。
