lacZ Reporter System as a Tool to Study Virulence Gene Regulation in Bacterial Pathogens.

β-galactosidase assay has been established as one of the most widely used reporters and can be effectually exploited to study promoter activity of Salmonella and other pathogens under various conditions. This method includes a preliminary stage of fusing the target promoter to a promoter-less lacZ gene encoding for the enzyme β-galactosidase. Supplementation of the synthetic ONPG substrate results in the accumulation of a chromogenic product proportionally to the activity of the fused promoter. Here we demonstrate the usage of this reporter system to study the regulation of the Salmonella Type three secretion system effector gene sseL in S. Typhimurium [1].