A moving DNA replication factory in Caulobacter crescentus

The in vivo intracellular location of components of the Caulobacter replica tion apparatus was visualized during the cell cycle. Replisome assembly occ urs at the chromosomal origin located at the stalked cell pole, coincident with the initiation of DNA replication. The replisome gradually moves to mi dcell as DNA replication proceeds and disassembles upon completion of DNA r eplication. Although the newly replicated origin regions of the chromosome are rapidly moved to opposite cell poles by an active process, the replisom e appears to be an untethered replication factory that is passively displac ed towards the center of the cell by the newly replicated DNA. These result s are consistent with a model in which unreplicated DNA is pulled into the replication factory and newly replicated DNA is bidirectionally extruded fr om the complex, perhaps contributing to chromosome segregation.