FIS is a nucleoid-associated protein in E. coli. It is highly expressed from fis gene from the end of the stationary phase till the mid-exponential phase. It is a DNA binding protein. It affects the topology and supercoiling of E. coli chromosome, and it regulates the expression of many other genes.
Travers, A.; Schneider, R.; Muskhelishvili, G. (2001). "DNA supercoiling and transcription in Escherichia coli: The FIS connection". Biochimie 83 (2): 213–7. doi:10.1016/S0300-9084(00)01217-7. PMID 11278071.