Spatial Distribution of H-NS in E. coli under Environmental Stress

Abstract

The heat-stable nucleoid structuring (H-NS) protein is an abundant DNA-binding protein in gram-negative bacteria. H-NS impacts both DNA condensation and globally regulates gene expression by binding to AT-rich domains of DNA. H-NS is known to play a key role in the adaptation of bacteria to thermal and osmotic shifts in the environment, although the mechanism is still poorly understood. In this study, we probed the spatial redistribution of H-NS in E. coli via super-resolved microscopy in response to osmotic stress and cold-shock at two phases of bacterial growth: exponential and stationary phase. While we saw little effect under conditions of cold-shock, we observed that in early stationary phase, under osmotic stress, H-NS markedly alters its intracellular organization, detaching from a tightly condensed chromosome, and moving toward the periphery of the cell. This response by H-NS to osmotic shock, notably, is not observed in exponential phase despite a similar condensation of the chromosomal DNA. To understand this observation we have been exploring the response of H-NS to other key regulators of the osmotic stress response.