Fine structure of the Deinococcus radiodurans nucleoid revealed by cryoelectron microscopy of vitreous sections
Fine structure of the Deinococcus radiodurans nucleoid revealed by cryoelectron microscopy of vitreous sections
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DOI：
10.1128/jb.187.23.8047-8054.2005
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发表时间：
2005-12-01
影响因子：
3.2
通讯作者：
Dubochet, J
中科院分区：
文献类型：
--
作者：
Eltsov, M;Dubochet, J
透射电子显微镜显示，极耐辐射细菌耐辐射球菌的类核可能具有不寻常的环状形状。这导致了一种假设，即耐辐射金黄色葡萄球菌基因组的紧密环形包装可能通过阻止双链DNA断裂末端的扩散而导致辐射抗性。要检验这一假说，必须确定DNA在类核中的分子排列，而用传统的电子显微镜方法是无法辨别的。我们应用了玻璃体切片的冷冻电子显微镜，发现耐辐射金黄色葡萄球菌的DNA排列不同于环形假脱机。呈指数增长的耐辐射金黄色葡萄球菌的弥漫珊瑚类核不显示任何特定的分子顺序。电子致密颗粒一般在类核的中心观察到。在稳定期细胞中，类核从细胞质中分离出来，DNA细丝局部平行排列，随着长时间饥饿，胆固醇型液晶相的数量增加。讨论了观察到的类核组织与耐辐射葡萄球菌的辐射抗性的关系。
Transmission electron microscopy revealed that the nucleoid of the extremely radioresistant bacteria Deinococcus radiodurans may adopt an unusual ring shape. This led to the hypothesis that the tight toroidal package of the D. radiodurans genome might contribute to radioresistance by preventing diffusion of ends of double-stranded DNA breaks. The molecular arrangement of DNA in the nucleoid, which must be determined to test this hypothesis, is not discernible by conventional methods of electron microscopy. We have applied cryoelectron microscopy of vitreous sections and found that the DNA arrangement in D. radiodurans differs from toroidal spooling. Diffuse coralline nucleoids of exponentially growing D. radiodurans do not reveal any particular molecular order. Electron-dense granules are generally observed in the centers of nucleoids. In stationary-phase cells, the nucleoid segregates from cytoplasm and DNA filaments show locally parallel arrangements, with increasing aspects of cholesteric liquid crystalline phase upon prolonged starvation. The relevance of the observed nucleoid organization to the radiation resistance of D. radiodurans is discussed.