IPTG is an inducer of beta-Galactosidase (X-Gal) in bacteria. It may be used with X-Gal in media to select recombinants by detecting M13 phage vectors beta-Galactosidase-positive blue colonies by transduction and pUC vectors by transformation into lacZ- host cells. IPTG is an inducer of the lac and tac promoters.