Ultrastructural analysis of differentiation in Legionella pneumophila
Ultrastructural analysis of differentiation in Legionella pneumophila
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DOI：
10.1128/jb.184.24.7025-7041.2002
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发表时间：
2002-12-01
影响因子：
3.2
通讯作者：
Garduño, RA
中科院分区：
文献类型：
--
作者：
Faulkner, G;Garduño, RA
嗜肺军团菌是一种适应性病原体，它在根本不同的宿主（淡水原生动物和哺乳动物细胞）的细胞内环境中复制，并且能够在宿主之间在水中长期饥饿中生存。对这些相当多样化的环境的生理适应似乎伴随着形态学变化（Garduno等人，第82-85页，见Marre等人，编辑，Legionella，2001），并且可以想象涉及发育分化。沿着L.通过体外和体内生长周期，我们现在已经发现这种细菌显示出前所未有的数量的形态形式，如透射电子显微镜的切片和冷冻断裂复制品所示。许多形式的细胞被膜的明显的超微结构特性，其中包括膜小叶的相对不透明性，囊泡形成，和/或丰富的内膜内陷的变化进行了鉴定。这些变化最好用图像分析软件记录，以获得横截面中包络的强度迹线。同样突出的是膜内颗粒分布的变化（在冷冻断裂标本的复制品中清楚地显示）和细胞质内含物的形成。我们的结果证实L. pneumophila是一种高度多形性的细菌，并澄清了一些早期的观察，表明产孢分化在L。嗜肺菌由于形态变化发生在生长周期内的保守序列中，我们的结果也为L.嗜肺性肺炎可能伴随着深刻的生理变化和阶段特异性的基因表达模式。
Legionella pneumophila is an adaptive pathogen that replicates in the intracellular environment of fundamentally divergent hosts (freshwater protozoa and mammalian cells) and is capable of surviving long periods of starvation in water when between hosts. Physiological adaptation to these quite diverse environments seems to be accompanied by morphological changes (Garduno et al., p. 82-85, in Marre et al., ed., Legionella, 2001) and conceivably involves developmental differentiation. In following the fine-structural pathway of L. pneumophila through both in vitro and in vivo growth cycles, we have now discovered that this bacterium displays an unprecedented number of morphological forms, as revealed in ultrathin sections and freeze-fracture replicas for transmission electron microscopy. Many of the forms were identified by the obvious ultrastructural properties of their cell envelope, which included changes in the relative opaqueness of membrane leaflets, vesiculation, and/or profuse invagination of the inner membrane. These changes were best documented with image analysis software to obtain intensity tracings of the envelope in cross sections. Also prominent were changes in the distribution of intramembranous particles (clearly revealed in replicas of freeze-fractured specimens) and the formation of cytoplasmic inclusions. Our results confirm that L. pneumophila is a highly pleomorphic bacterium and clarify some early observations suggesting sporogenic differentiation in L. pneumophila. Since morphological changes occurred in a conserved sequence within the growth cycle, our results also provide strong evidence for the existence of a developmental cycle in L. pneumophila that is likely accompanied by profound physiological alterations and stage-specific patterns of gene expression.