[1] Fis was originally identified as the factor for inversion stimulation of the homologous Hin and Gin site-specific DNA recombinases of Salmonella and phage Mu, respectively.

This small, basic, DNA-bending protein has recently been shown to function in many other reactions including phage lambda site-specific recombination, transcriptional activation of rRNA and tRNA operons, repression of its own synthesis, and oriC-directed DNA replication.

[3] Fis is a very important small nucleotide-associated protein which plays a role in affecting the bacterial chromosome structure and the initiation of DNA replication.

[4] It is a nucleoid-associated protein in Escherichia coli that is abundant during early exponential growth in rich medium but is in short supply during stationary phase.

[7] The Fis nucleoid protein is differentiated by its fast increase in synthesis rates following nutrient upshifts and its abundance in rapidly growing E. coli cells.

Formation of a supposed RNA secondary structure element beginning 50 nucleotides upstream of the AUG also positively affects fis translation by up to 10 fold.

combined A repressive effect of Fis and previously characterized negative regulatory factors could be responsible to keep the gene silenced most of the time.

In addition to bringing about overall downregulation of the Mu genome, it also ensures silencing of the advantageous but potentially lethal mom gene.

Fis is also involved in the regulation of a range of genes in bacterial species such as P. multocida, Enteroaggregative Escherichia coli,[13] similar organisms.

It is possible that the elevated expression of Fis is important in the adaptation of P. putida during colonization of plant roots by promoting biofilm formation when the migration of bacteria is no longer advantageous.