Effect of O side-chain length and composition on the virulence of Shigella flexneri 2a.
Effect of O side-chain length and composition on the virulence of Shigella flexneri 2a.
复制标题
O侧链长度和组成对福氏志贺氏菌2a毒力的影响。
DOI：
10.1111/j.1365-2958.1996.tb02656.x
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发表时间：
1996
影响因子：
3.6
通讯作者：
Maurelli,AT
中科院分区：
文献类型：
--
作者：
Sandlin,RC;Goldberg,MB;Maurelli,AT
福氏志贺菌的IcsA是细胞间扩散所必需的，位于细菌一极的外膜上，在那里它催化宿主细胞肌动蛋白的聚合。肌动蛋白尾部的形成提供了使细菌以单向方式穿过宿主细胞质的力。我们之前已经证明，福氏志贺菌2a的粗脂多糖（LPS）突变体是无毒的，不能在组织培养单层中形成斑块。这种无法形成斑块的情况与IcsA的非极性定位和宿主细胞膜突起形成（“烟花”）的丧失有关。为了定义烟花形成所需的最小LPS结构，我们构建了含有编码0侧链聚合酶的inrfc突变的福氏志贺菌菌株（BS 497）和由于inrfaL突变而具有缺陷0侧链连接酶的菌株BS 520 JS 497产生由具有0侧链的一个重复单元的核心组成的LPS，而BS 520产生由没有O侧链的完整核心组成的LPS。BS497仍具有侵袭性，但在组织培养单层中未形成烟花或斑块，并且在Serény试验中呈阴性。BS520具有侵入性，产生的短烟花数量减少，并产生微小的斑块，但在Serény测试中呈阴性。用抗IcsA抗体分析BS497证明IcsA分布在整个细胞表面。IcsA在BS 520表面上的分布主要是单极的，IcsA标记沿着细菌的侧面有一些痕迹。当对感染的单层细胞进行聚合肌动蛋白染色时，也可以看到类似的模式。这些结果表明，O侧链的存在和长度对于IcsA在极点的适当定位或维持都很重要，这随后影响形成肌动蛋白尾部和产生烟花的能力。这种形成肌动蛋白尾和烟花的能力降低导致志贺氏菌移动到邻近宿主细胞的能力降低。为了确定O侧链的糖组成是否对形成烟花的能力很重要，将福氏志贺菌2a的fb区替换为大肠杆菌血清型O8或O25的fb区。两种杂交体均具有侵袭性，形成斑块，并产生阳性Serény反应。这些结果表明，与LPS长度不同，O侧链的糖组成不是IcsA适当定位和有效细胞间运动的关键要求。
IcsA ofShigella flexneriis required for intercellular spread and is located in the outer membrane at one pole of the bacterium, where it catalyses the polymerization of host‐cell actin. The formation of the actin tail provides the force to move the bacterium in a unidirectional manner through the host‐cell cytoplasm. We have previously demonstrated that rough lipopolysaccharide (LPS) mutants of S.flexneri2a are avirulent and cannot form plaques in tissue‐culture monolayers. This inability to form plaques is associated with non‐polar localization of IcsA and loss of host‐cell membrane‐protrusion formation ('fireworks'). To define the minimal LPS structure required for fireworks formation, we constructed a strain of S.flexneri(BS497) that contains a mutation inrfc, encoding the O side‐chain polymerase, and a strain, BS520, that possesses a defective O side‐chain ligase due to a mutation inrfaL.BS497 produces a LPS that consists of a core with one repeat unit of the O side‐chain, while BS520 produces a LPS consisting of a complete core with no O side‐chain. BS497 remained invasive but did not form fireworks or plaques in tissue‐culture monolayers and was negative in the Serény test. BS520 was invasive, generated reduced numbers of short fireworks, and made tiny plaques, but it was negative in the Serény test. Analysis of BS497 with anti‐lcsA antibody demonstrated that IcsA was distributed over the entire cell surface. The distribution of IcsA on the surface of BS520 was predominantly unipolar, with some trail‐back of IcsA label along the sides of the bacterium. A similar pattern was seen when infected monolayers were stained for polymerized actin. These results suggest that both the presence and the length of the O side‐chain are important in the proper localization or maintenance of IcsA at the pole which subsequently affects the ability to form actin tails and produce fireworks. This reduced ability to form actin tails and fireworks results in a decreased ability ofShigellato move into adjacent host cells. To determine if the sugar composition of the O side‐chain is important in the ability to form fireworks, therfbregion of S.flexneri2awas replaced with therfbregion fromEscherichia collserotype O8 or O25. Both hybrids were invasive, formed plaques, and gave positive Serény reactions. These results suggest that, unlike LPS length, the sugar composition of the O side‐chain is not a critical requirement for the proper localization of IcsA and efficient intercellular movement.