James Pelletier1, Ken Halvorsen2, Wesley Wong2, Suckjoon Jun1*
1FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
?2Rowland Institute at Harvard University, Cambridge, MA 02142?Email: firstname.lastname@example.org
Before an Escherichia coli cell divides to give two viable daughters, the cell must replicate, decatenate, and segregate its genetic materials. To gain intuition and to investigate the physical mechanisms underlying these processes during the cell cycle, we have employed a high-throughput PDMS microfluidic device and optical tweezers – the micropiston – to isolate and manipulate ex vivo/in vitro bacterial chromosomes in strong confinement. We present the dynamics of expansion of the bacterial chromosomes upon release from the cell, as well as their force-compression (as opposed to force-stretching) curves in strong confinement. Furthermore, we show that simple physical models based on the entropic spring in strong confinement explain the experimental data remarkably well; the isolated bacterial chromosome in the micropiston behaves like a loaded entropic spring. This is the first experimental study of its kind, which provides a key physical insight into organization and segregation of chromosomes in bacteria as well as eukaryotes.
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