RT Journal Article SR Electronic T1 Cell boundary confinement sets the size and position of the E. coli chromosome JF bioRxiv FD Cold Spring Harbor Laboratory SP 348052 DO 10.1101/348052 A1 Fabai Wu A1 Pinaki Swain A1 Louis Kuijpers A1 Xuan Zheng A1 Kevin Felter A1 Margot Guurink A1 Debasish Chaudhuri A1 Bela Mulder A1 Cees Dekker YR 2018 UL http://biorxiv.org/content/early/2018/06/15/348052.abstract AB While the spatiotemporal structure of the genome is crucial to its biological function, many basic questions remain unanswered on the morphology and segregation of chromosomes. Here, we experimentally show in Escherichia coli that spatial confinement plays a dominant role in determining both the chromosome size and position. In non-dividing cells with lengths up to 10 times normal, single chromosomes are observed to expand more than 4 fold in size, an effect only modestly influenced by deletions of various nucleoid-associated proteins. Chromosomes show pronounced internal dynamics but exhibit a robust positioning where single nucleoids reside strictly at mid-cell, while two nucleoids self-organize at ¼ and ¾ cell positions. Molecular dynamics simulations of model chromosomes recapitulate these phenomena and indicate that these observations can be attributed to depletion effects induced by cytosolic crowders. These findings highlight boundary confinement as a key causal factor that needs to be considered for understanding chromosome organization.