Biophysical Society Thematic Meeting| Les Houches 2019

Multiscale Modeling of Chromatin: Bridging Experiment with Theory

Poster Abstracts

18-POS Board 18 GROWTH PHASE DEPENDENT CHROMOSOME CONDENSATION AND H-NS PROTEIN REDISTRIBUTION IN E. COLI UNDER OSMOTIC STRESS Joshua Milstein 1 ; Nafiseh Rafiei 2 ; Martha Cordova 3 ; William Navarre 3 ; 1 University of Toronto, Department of Physics, Toronto, Ontario, Canada 2 University of Toronto, IBBME, Toronto, Ontario, Canada 3 University of Toronto, Department of Molecular Genetics, Toronto, Ontario, Canada The heat-stable nucleoid-structuring (H-NS) protein is a global transcriptional regulator implicated in coordinating the expression of over 200 genes in E. coli bacteria. We have applied a combination of super-resolved microscopies to quantify the intracellular, spatial reorganization of H-NS in response to osmotic stress. We find that H-NS shows a growth phase dependent response to osmotic shock. In logarithmic phase, H-NS detaches from a tightly compacted bacterial chromosome and is excluded from the nucleoid volume. Such behaviour is completely absent in exponential phase but may be induced by exposing the culture to the DNA gyrase inhibitor coumermycin. This observation implies that the osmotic stress response in E. coli is coordinated in part by the level of supercoiling in the bacterial chromosome.

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