Kahng Lyn Sue, Shapiro Lucy
Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
J Bacteriol. 2003 Jun;185(11):3384-91. doi: 10.1128/JB.185.11.3384-3391.2003.
The origins of replication of many different bacteria have been shown to reside at specific subcellular locations, but the mechanisms underlying their positioning and segregation are still being elucidated. In particular, little is known about the replication of multipartite genomes in bacteria. We determined the cellular positions of the origins of the replicons in the alpha proteobacteria Agrobacterium tumefaciens and Sinorhizobium meliloti and found that they are located at the poles of the cells. Our work demonstrates the conserved extreme polar localization of circular chromosome origins in these alpha proteobacteria and is also the first to specify the cellular location of origin regions from the repABC family. The cellular location of a derivative of the RK2 plasmid is distinct from that of the alpha proteobacterium genomic replicon origins but is conserved across bacteria. Colocalization experiments with the genomic replicons of A. tumefaciens revealed that the repABC replicons, although preferentially positioned at the cell pole, colocalize only rarely. For the repABC replicons in this organism, occupying discrete spatial locations may contribute to their coexistence and stable inheritance.
许多不同细菌的复制起点已被证明位于特定的亚细胞位置，但其定位和分离的潜在机制仍在阐明之中。特别是，关于细菌中多部分基因组的复制知之甚少。我们确定了α-变形菌根癌土壤杆菌和苜蓿中华根瘤菌中复制子复制起点的细胞位置，发现它们位于细胞的两极。我们的工作证明了这些α-变形菌中环状染色体起点的保守极端极性定位，也是首次明确来自repABC家族的起点区域的细胞位置。RK2质粒衍生物的细胞位置与α-变形菌基因组复制起点不同，但在细菌中是保守的。根癌土壤杆菌基因组复制子的共定位实验表明，repABC复制子虽然优先定位在细胞极，但很少共定位。对于该生物体中的repABC复制子，占据离散的空间位置可能有助于它们的共存和稳定遗传。
