Increased Temperature Influences hilA Gene Fusion Expression in a Salmonella Typhimurium Poultry Isolate

Entry of a pathogen into a warm-blooded host can be accompanied by an increase in temperature. Therefore, it is expected that heat shock genes could play an important role in bacterial infection. The gene hilA encodes for a transcriptional regulator and is essential for S. Typhimurium invasion. In the current study, we generated a transcriptional fusion between the promoter of hilA and the gene gfp[LVA] encoding for a mutant GFP with a half-life of 40 min to observe the effect of heat as a stressor in activating hilA in Salmonella. -galactosidase assays were also conducted to verify the expression of hilA under the investigated conditions. The highest induction of hilA (3.38 fold) was observed after 1 h of heat treatment (45C) as measured by the hilA-gfp[LVA] fusion construct. The cell transfer back to 37C resulted in a gradual decrease in hilA expression and no detectable induction after 2 h. Based on the activity of -galactosidase, heat treatment of S. Typhimurium hilA::lacZY fusion strain at 45C was found to induce the expression of hilA 1.56 fold. The data demonstrates that elevated temperature may be an inducer of hilA expression. More studies including broader range of temperatures and conditions are needed to better characterize the influence of temperature increases on Salmonella pathogenicity.