The Escherichia coli chromosome is organized with the left and right chromosome arms in separate cell halves

Abstract

SummaryWe have developed a system for the simultaneous labelling of two specific chromosomal sites using two different fluorescent ParB/parS systems. Using this, we demonstrate that the two chromosome arms are spatially arranged in newborn cells such that markers on the left arm of the chromosome lie in one half of the cell and markers on the right arm of the chromosome lie in the opposite half. This is achieved by reorganizing the chromosome arms of the two nucleoids in pre-division cells relative to the cell quarters. The spatial reorganization of the chromosome arms ensures that the two replication forks remain in opposite halves of the cell during replication. The relative orientation of the two reorganized nucleoids in pre-division cells is not random. Approximately 80% of dividing cells have their nucleoids oriented in a tandem configuration.

Colocalization of distant chromosomal loci in space in E. coli: a bacterial nucleolus

“…The separation of oriC from ter in space (Fig. 2H) has been reported previously (Nielsen et al 2006).…”

“…In order to examine the relative positions of the rRNA operons in space, we adapted a previously described system using two different ParB homologs, each of which binds to a different DNA sequence (parS site) inserted next to an rRNA operon (Nielsen et al 2006). The ParB protein that binds to one of these sites was fused to cyan fluorescent protein (CFP), and the ParB that binds to the other parS site was fused to yellow fluorescent protein (YFP).…”

Short-time movement of E. coli chromosomal loci depends on coordinate and subcellular localization

“…Some studies of the bacterial chromosome 3 have focussed on the organizational properties valid at particular times, for example, by taking the statistics of the subcellular positioning of loci within a population [8][9][10][11][12][13] . Other studies measure more directly the variation in time of chromosomal organization, which is fundamentally interconnected with chromosome replication and segregation.…”

Spatio-Temporal Organization of Replication in Bacteria and Eukaryotes (Nucleoids and Nuclei)

“…In cells with a single chromosome, the origin resides at mid-cell with the left and right chromosome arms in opposite cell halves (Fig. 1B) (Nielsen et al 2006;Wang et al 2006). The terminus region appears to connect the two arms to complete the circle.…”

“…With the replication machinery following the track of the nucleoid, it stands to reason that the replication process itself could serve as a key player in setting up the organization of the resulting sister chromatids. Indeed, recent work in E. coli suggests that replication along the nucleoid and the coupled segregation and compaction of the newly replicated DNA helps to reproduce the same nucleoid pattern in the daughter cells (Nielsen et al 2006;Wang et al 2006). discussion of spatial and temporal control of DNA replication in eukaryotes will be restricted to the S phase of the cell cycle.…”