Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, The Netherlands.
Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125, USA.
Nat Commun. 2019 May 16;10(1):2194. doi: 10.1038/s41467-019-10221-0.
Although the physical properties of chromosomes, including their morphology, mechanics, and dynamics are crucial for their biological function, many basic questions remain unresolved. Here we directly image the circular chromosome in live E. coli with a broadened cell shape. We find that it exhibits a torus topology with, on average, a lower-density origin of replication and an ultrathin flexible string of DNA at the terminus of replication. At the single-cell level, the torus is strikingly heterogeneous, with blob-like Mbp-size domains that undergo major dynamic rearrangements, splitting and merging at a minute timescale. Our data show a domain organization underlying the chromosome structure of E. coli, where MatP proteins induce site-specific persistent domain boundaries at Ori/Ter, while transcription regulators HU and Fis induce weaker transient domain boundaries throughout the genome. These findings provide an architectural basis for the understanding of the dynamic spatial organization of bacterial genomes in live cells.
尽管染色体的物理性质，包括其形态、力学和动力学对于其生物学功能至关重要，但仍有许多基本问题尚未解决。在这里，我们通过扩展细胞形状，直接对活大肠杆菌中的圆形染色体进行成像。我们发现，它呈现出环形拓扑结构，平均而言，复制起点的密度较低，复制终点是一段超薄的灵活 DNA 字符串。在单细胞水平上，环形结构明显具有异质性，存在类似于 Mbp 大小的团块域，这些团块域会发生重大的动态重排，在微小的时间尺度上分裂和融合。我们的数据显示了大肠杆菌染色体结构的一种域组织，其中 MatP 蛋白在 Ori/Ter 处诱导特定的持久域边界，而转录调节剂 HU 和 Fis 则在整个基因组中诱导较弱的瞬时域边界。这些发现为理解活细胞中细菌基因组的动态空间组织提供了结构基础。
