Coordination between replication, segregation and cell division in multi-chromosomal bacteria: lessons from Vibrio cholerae

Bacteria display a highly flexible cell cycle in which cell division can be temporally disconnected from the replication/segregation cycle of their genome. The accuracy of genetic transmission is enforced by restricting the assembly of thecell division apparatus to the low DNA-density zones that develop between the regularly spaced nucleoids originating from theconcurrent replication and segregation of genomic DNA. In most bacteria, the process is simplified because the genome is encodedon a single chromosome. This is notably the case in Escherichia coli, the most well studied bacterial model organism. However,~10% of bacteria have domesticated horizontally acquired mega-plasmids into extra-numerous chromosomes. Most of our currentknowledge on the cell cycle regulation of multi-chromosomal species derives from the study of replication, segregation and celldivision in Vibrio cholerae, the agent of the deadly epidemic human diarrheal disease cholera. A nicety of this model is that it isclosely related to E. coli in the phylogenetic tree of bacteria. Here, we review recent findings on the V. cholerae cell cycle in thecontext of what was previously known on the E. coli cell cycle.