Fis is required for full induction of chromosomal S. typhimurium hilA : : Tn5lacZY expression .
Using a genetic approach , Fis was shown to be necessary for the induction of hilA expression , genes .
Fis is involved in SPI expression Positive regulation of SPI-1 genes by Fis was expected considering the fact that hilA , is upregulated by Fis .
Expression of hilA is increased by the Factor for Inversion Stimulation , Fis .