Multiple large filament bundles observed in Caulobacter crescentus by electron cryotomography
Multiple large filament bundles observed in Caulobacter crescentus by electron cryotomography
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DOI：
10.1111/j.1365-2958.2006.05355.x
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发表时间：
2006-10-01
影响因子：
3.6
通讯作者：
Jensen, Grant J.
中科院分区：
文献类型：
--
作者：
Briegel, Ariane;Dias, D. Prabha;Jensen, Grant J.
虽然没有任何细胞骨架曾经被认为是原核生物的一个显著特征，但现在很清楚，许多不同的细菌蛋白质确实在体内形成细丝。尽管这些蛋白质在细胞形状，基因组分离和细胞分裂中发挥着关键作用，但分子机制仍然不清楚，部分原因是缺乏电子显微镜分辨率图像，可以看到这些细丝在其细胞环境中起作用。在这里，电子cryotomography被用来成像广泛研究的模型原核生物Caulobacter crescentus在一个完整的，接近天然的状态，产生这些细胞的三维重建与前所未有的清晰度和保真度。我们观察到许多情况下，在不同的位置在整个细胞和细胞周期的不同阶段的大丝束。根据形状和位置，束似乎分为四个主要类别，这里称为“内弯曲”，“胞质”，“极性”和“环状”。在试图识别至少一些细丝的过程中，我们对不存在新月体和MreB细丝的细胞进行成像。内曲率和胞质束持续存在，连同它们的定位模式，表明它们是由尚未鉴定的细胞骨架蛋白。因此，细菌丝状体经常被发现成束，它们的多样性和丰度比以前怀疑的要大。
While the absence of any cytoskeleton was once recognized as a distinguishing feature of prokaryotes, it is now clear that a number of different bacterial proteins do form filaments in vivo. Despite the critical roles these proteins play in cell shape, genome segregation and cell division, molecular mechanisms have remained obscure in part for lack of electron microscopy-resolution images where these filaments can be seen acting within their cellular context. Here, electron cryotomography was used to image the widely studied model prokaryote Caulobacter crescentus in an intact, near-native state, producing three-dimensional reconstructions of these cells with unprecedented clarity and fidelity. We observed many instances of large filament bundles in various locations throughout the cell and at different stages of the cell cycle. The bundles appear to fall into four major classes based on shape and location, referred to here as 'inner curvature', 'cytoplasmic', 'polar' and 'ring-like'. In an attempt to identify at least some of the filaments, we imaged cells where crescentin and MreB filaments would not be present. The inner curvature and cytoplasmic bundles persisted, which together with their localization patterns, suggest that they are composed of as-yet unidentified cytoskeletal proteins. Thus bacterial filaments are frequently found as bundles, and their variety and abundance is greater than previously suspected.