Alternate name: BCIG. X-GlcU (5-Bromo-4-chloro-3-indolyl-β-D-glucuronide, cyclohexylammonium salt) is a chromogenic β-glucuronidase substrate widely used for monitoring E. coli contamination in food (such as meat, dairy products and shellfish, etc) and water, and for the detection of GUS gene expression in plants.