Teleman A A, Graumann P L, Lin D C, Grossman A D, Losick R
Department of Molecular and Cellular Biology The Biological Laboratories Harvard University Cambridge, Massachusetts 02138, USA.
Curr Biol. 1998 Oct 8;8(20):1102-9. doi: 10.1016/s0960-9822(98)70464-6.
The contour length of the circular chromosome of bacteria is greater than a millimeter but must be accommodated within a cell that is only a few micrometers in length. Bacteria do not have nucleosomes and little is known about the arrangement of the chromosome inside a prokaryotic cell.
We have investigated the arrangement of chromosomal DNA within the bacterium Bacillus subtilis by using fluorescence microscopy to visualize two sites on the chromosome simultaneously in the same cell. Indirect immunofluorescence with antibodies against the chromosome partition protein Spo0J were used to visualize the replication origin region of the chromosome. Green fluorescent protein fused to the lactose operon repressor Lacl was used to decorate tandem copies of the lactose operon operator lacO. A cassette of tandem operators was separately inserted into the chromosome near the origin (359 degrees), near the replication terminus (181 degrees), or at two points in between (90 degrees and 270 degrees). The results show that the layout of the chromosome is dynamic but is principally arranged with the origin and terminus maximally apart and the quarter points of the chromosome in between.
The use of cytological methods to visualize two chromosomal sites in the same cell has provided a glimpse of the arrangement of a bacterial chromosome. We conclude that, to a first approximation, the folding of the bacterial chromosome is consistent with, and may preserve, the linear order of genes on the DNA.
细菌环状染色体的轮廓长度大于一毫米，但必须容纳在长度仅为几微米的细胞内。细菌没有核小体，关于原核细胞内染色体的排列知之甚少。
我们通过荧光显微镜在同一细胞中同时可视化染色体上的两个位点，研究了枯草芽孢杆菌内染色体DNA的排列。使用针对染色体分配蛋白Spo0J的抗体进行间接免疫荧光，以可视化染色体的复制起始区域。与乳糖操纵子阻遏物Lacl融合的绿色荧光蛋白用于标记乳糖操纵子操纵基因lacO的串联拷贝。将串联操纵基因盒分别插入染色体上靠近起始点（359度）、靠近复制终点（181度）或两者之间的两个点（90度和270度）。结果表明，染色体的布局是动态的，但主要是将起始点和终点最大限度地分开，并将染色体的四分之一点置于两者之间。
使用细胞学方法在同一细胞中可视化两个染色体位点，让我们得以一窥细菌染色体的排列。我们得出结论，初步近似地说，细菌染色体的折叠与DNA上基因的线性顺序一致，并且可能保留了这种顺序。
