Bromo-4-chloro-3-indolyl-b-D-galactoside (X-Gal) research grade X-Gal is a well known histochemical substrate used to detect the β-galactosidase enzyme (1, 2, 3, 4, 9, 10). Identification of lacf-colonies (8). X-gal is used to distinguish recombinant plasmids from parental vectors in cloning ex