Salmonella Enterica Serovar Typhimurium HilA-LacZY Fusion Gene Response to Iron Chelation or Supplementation in Rich and Minimal Media

Abstract

Virulence expression of Salmonella enterica serovar Typhimurium under iron limited condition was measured by β-galactosidase (β-gal) assay using a hilA-lacZY fusion strain and calculated as Miller units. hilA-lacZY β-galactosidase assays were performed in brain heart infusion (BHI) and minimal media (M9), after iron chelation with 2, 2-dipridyl and iron-supplementation respectively. Before performing virulence assays, concentrations of iron in the media were estimated using ferrozine. Iron content was found to be more in BHI (42.6 µg dL⁻¹) as compared to M9 (10.03 µg dL⁻¹). β-gal activity of Salmonella Typhimurium in BHI was generally less than that observed in M9. After exposure to various combinations of iron chelator in BHI, hilA-lacZY activity only increased at the highest concentration of chelator (200 µM) but decreased in M9 media for all iron concentrations when compared to controls with no iron amendment. These results indicate that iron availability may influence S. Typhimurium hilA expression.

Keywords:

• HilA gene
• Expression
• Iron
• Salmonella Typhimurium

Acknowledgments

This research was partially supported (S. C. Ricke) by Hatch grant H8311 administered by the Texas Agricultural Experiment Station and USDA-NRI grant number 2001-02675. The authors wish to thank C. A. Lee (Department of Microbiology and Molecular Genetics, Harvard Medical School) for providing the hilAlacZY fusion strain and Department of Biotechnology, Ministry of Science and Technology, India for awarding DBT overseas Associate Fellowship to Dr. P. Rishi.