from Georgi Muskhelishvili and Andrew Travers writing in Bacterial Gene Regulation and Transcriptional Networks:
In the bacterial nucleoid different configurations of negatively supercoiled DNA are constrained by different NAPs. Thus while H-NS can constrain, by bridging, the interwindings of plectonemic structure, HU induces a left-handed coiled configuration while FIS can bind within DNA loops. The topological and dynamic interconvertibility of these structures contributes substantially to the regulation of gene expression in bacteria. We review here some of the mechanisms involved and argue that they form the basis for a coordination of gene transcription which results in the establishment of a single interconnected heterarchical control system that is responsible both for maintaining, when appropriate, a homoeostatic control of growth and also for mediating transitions between different cellular physiological states.
Further reading: Bacterial Gene Regulation and Transcriptional Networks