Escherichia coli Chromosomes in the Crowded Cellular Environment

\In spite of our detailed knowledge of the enzymology of DNA replication and of the topology of gene expression, we do not understand how, on a larger scale, bacterial DNA is organized within cell or nucleoid. Also, in the process of [bacterial DNA] segregation, we hardly know what force(s) move the newly replicated DNA strands faithfully to the prospective daughter cells." --- Conrad L. Woldringh To provide insights and answers in response to these questions, we have designed pressure actuated micro uidic valves based on a PDMS lab-on-a-chip platform. Using this device, we mechanically perturb the main macromolecular structures in Escherichia coli, and monitor the individual phenotypic responses in real time. Meanwhile, we also utilized the mothermachine design and rened it suiting E. coli cells in particular growth conditions. In the mother-machine devices, we apply osmotic shocks to the cells. We nd mechanical perturbations decrease the cytoplasmic cell volume, which in turn causes the compactness of nucleoid to increase and the chromosome-cytoplasm phase separation to be more abrupt; meanwhile, the chromosome-free regions between adjacent separated nucleoids and at cell poles persist. Furthermore, with an ardent perturbation, nucleoids are rarely bisected; nevertheless, mild perturbations often displace nucleoids after a period of deforming them. I also discuss the possibility to observe the effect of the hypothesized co-transcriptional translation transertion and our results which potentially indicate that.