Redefining the requisite lipopolysaccharide structure in Escherichia coli
Redefining the requisite lipopolysaccharide structure in Escherichia coli
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DOI：
10.1021/cb0500015
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发表时间：
2006-01-01
影响因子：
4
通讯作者：
Woodard, Ronald W.
中科院分区：
文献类型：
--
作者：
Meredith, Timothy C.;Aggarwal, Parag;Woodard, Ronald W.
革兰氏阴性细菌在细胞壁外膜(OM)周围有一层不对称的脂双层。OM内叶主要由各种甘油磷脂组成，而外叶主要含有独特的两亲性大分子--脂多糖(内毒素或内毒素)。大多数革兰氏阴性菌都产生含有至少一个2-酮-3-脱氧-D-甘露-辛磺酸盐(Kdo)分子的内毒素。长期以来，人们一直认为，大肠杆菌生长所需的最小内毒素结构是两个Kdo残基，附着在脂质A上，将生存能力与毒性联系在一起。在这里，我们报告了无条件的E.ColiK-12抑制株KPM22的构建和特性，KPM22缺乏Kdo，尽管主要是阐述内毒素非活性的内毒素前体脂蛋白IVA，但仍然活着。我们的结果挑战了已建立的大肠杆菌Kdo(2)-脂质A教条，表明以前观察到的和有充分文献记载的细胞活力对Kdo合成的依赖源于碳水化合物耗尽后沉淀的致命的多营养，而不是Kdo分子本身作为OM LPS层不可或缺的结构成分的内在需要。在营养缺陷型亲本菌株中，将内膜转运子MSBA包含在多拷贝质粒上可以部分抑制致死的Delta Kdo表型，这表明增加非糖化脂质A转运率可以部分补偿Kdo的耗竭。脂类IVA OM的史无前例的性质重新定义了在大肠杆菌中生存所必需的内毒素结构。
Gram-negative bacteria possess an asymmetric lipid bilayer surrounding the cell wall, the outer membrane (OM). The OM inner leaflet is primarily composed of various glycerophospholipids, whereas the outer leaflet predominantly contains the unique amphiphilic macromolecule, lipopolysaccharide (LPS or endotoxin). The majority of all Gram-negative bacteria elaborate LPS containing at least one 2-keto 3-deoxy-D-manno-octulosonate (Kdo) molecule. The minimal LPS structure required for growth of Escherichia coli has long been recognized as two Kdo residues attached to lipid A, inextricably linking viability to toxicity. Here we report the contruction and characterization of the nonconditional E.coli K-12 suppressor strain KPM22 that lacks Kdo and is viable despite predominantly elaborating the endotoxically inactive LPS precursor lipid IVA. Our results challenge the established E. coli Kdo(2)-lipid A dogma, indicating that the previously observed and well-documented dependence of cell viability on the synthesis of Kdo stems from a lethal pleiotrophy precipitated after the depletion of the carbohydrate, rather than an inherent need for the Kdo molecule itself as an indispensable structural component of the OM LPS layer. Inclusion of the inner membrane LPS transporter MsbA on a multicopy plasmid partially suppresses the lethal Delta Kdo phenotype directly in the auxotrophic parent strain, suggesting increased rated of nonglycosylated lipid A transport can, in part, compensate for Kdo depletion. The unprecedented nature of a lipid IVA OM redefines the requisite LPS structure for viability in E.coli.