Growth Phase-Dependent Chromosome Condensation and Heat-Stable Nucleoid-Structuring Protein Redistribution in Escherichia coli under Osmotic Stress

Abstract

The heat-stable nucleoid-structuring (H-NS) protein coordinates the expression of over 200 genes in E. coli , with a large number involved in both bacterial virulence and drug resistance. We report on the novel observation of a dynamic compaction of the bacterial chromosome in response to exposure to high levels of salt. This stress response results in the detachment of H-NS proteins and their subsequent expulsion to the periphery of the cells. We found that this behavior is related to mechanical properties of the bacterial chromosome, in particular, to how tightly twisted and coiled is the chromosomal DNA. This behavior might act as a biomechanical response to stress that coordinates the expression of genes involved in adapting bacteria to a salty environment.