X-Gluc

X-Gluc (5-Bromo-4-chloro-3-indolyl-ß-D-glucuronide) is a carbohydrate that serves as a substrate for the reporter gene, ß-glucuronidase (GUSB). In the presence of the enzyme, X-Gluc is hydrolyzed to produce a clear blue product. This color change is the basis of the GUS reporter assay for analyzing promoter activity and gene expression, notably in plants. As ß-glucuronidase is natively expressed in E. coli, X-Gluc is also useful in detecting bacterial contamination in food, water, and the urinary tract.