Chromosome Replication and Segregation in Bacteria

Abstract

In dividing cells, chromosome duplication once per generation must be coordinated with faithful segregation of newly replicated chromosomes and with cell growth and division. Many of the mechanistic details of bacterial replication elongation are well established. However, an understanding of the complexities of how replication initiation is controlled and coordinated with other cellular processes is emerging only slowly. In contrast to eukaryotes, in which replication and segregation are separate in time, the segregation of most newly replicated bacterial genetic loci occurs sequentially soon after replication. We compare the strategies used by chromosomes and plasmids to ensure their accurate duplication and segregation and discuss how these processes are coordinated spatially and temporally with growth and cell division. We also describe what is known about the three conserved families of ATP-binding proteins that contribute to chromosome segregation and discuss their inter-relationships in a range of disparate bacteria.

Concerted control of Escherichia coli cell division

“…Importantly, the approach can be extended to infer how the division rate is affected by molecular variables governing the cell cycle, such as expression of key cell cycle regulators or other proxies of cell cycle stage (see SI Appendix, section S2, for a detailed discussion). In E. coli, these molecular players are well characterized, and obvious candidates are the coupled circuits involving genome replication (and prominently proteins such as DnaA, SeqA, and Hda) (24,25) and genome segregation and cell division (and proteins such as MinC-D-E, MukB, FtsK, and FtsZ) (26)(27)(28). Our full phenomenological characterization of cell division control poses the question of which of these molecules are carrying out the observed regulation and using which regulatory architectures.…”

The road to rack and ruin: selecting deleterious mitochondrial DNA variants

“…Moreover, in a laboratory strain of mice there was no evidence of intermolecular mtDNA recombination in the germ-line over the course of 50 generations [42]. An ability to resolve recombination junctions might be required at the end of the replication cycle as found for bacteria [43], and be necessary to regulate the networks of mtDNA molecules that form in adult human heart [44]. It is unlikely that mitochondria can create such DNA structures and yet be unable to resolve or otherwise process them.…”

Bacillus subtilischromosome organization oscillates between two distinct patterns

“…In eukaryotes, DNA replication, chromosome condensation, and sister chromatid segregation are separated into distinct steps in the cell cycle that are safeguarded by checkpoint pathways. In bacteria, these processes occur concurrently, posing unique challenges to genome integrity and inheritance (1,2). In the absence of temporal control, bacteria take advantage of spatial organization to promote faithful and efficient chromosome segregation.…”

“…In the absence of temporal control, bacteria take advantage of spatial organization to promote faithful and efficient chromosome segregation. The organization of the chromosome dictates where the chromosome is replicated, and the factors that organize and compact the newly replicated DNA play a central role in its segregation (1,2).…”