Yee Benjamin, Sagulenko Evgeny, Morgan Garry P, Webb Richard I, Fuerst John A
School of Chemistry and Molecular Biosciences, The University of Queensland St. Lucia, QLD, Australia.
Front Microbiol. 2012 Sep 13;3:326. doi: 10.3389/fmicb.2012.00326. eCollection 2012.
The nucleoid of the planctomycete Gemmata obscuriglobus is unique within the Bacteria in being both highly condensed and enclosed by a double-membrane nuclear envelope, seemingly analogous to the nucleus of eukaryotes. Here we have applied electron tomography to study high-pressure frozen, cryosubstituted cells of G. obscuriglobus and found multiple nested orders of DNA organization within the condensed nucleoid structure. Detailed examination of the nucleoid revealed a series of nested arcs characteristic of liquid crystalline cholesteric DNA structure. The finest fibers were arranged in parallel concentrically in a double-twist organization. At the highest order of nucleoid organization, several of these structures come together to form the core of the G. obscuriglobus nucleoid. The complex structure of DNA within this nucleoid may have implications for understanding the evolutionary significance of compartmentalized planctomycete cells.
在细菌中，球形芽殖菌（Gemmata obscuriglobus）的拟核是独一无二的，它高度浓缩并被双层膜核包膜所包围，似乎类似于真核生物的细胞核。在这里，我们应用电子断层扫描技术研究了高压冷冻、冷冻替代的球形芽殖菌细胞，发现在浓缩的拟核结构内存在多个嵌套层次的DNA组织。对拟核的详细检查揭示了一系列液晶胆甾型DNA结构特有的嵌套弧。最细的纤维以双螺旋结构平行且同心排列。在拟核组织的最高层次，这些结构中的几个聚集在一起形成了球形芽殖菌拟核的核心。这个拟核内DNA的复杂结构可能对理解具有区室化的芽殖菌细胞的进化意义有启示。
