The Effect of Glucose, Lactose, and Galactose on the Induction of β- Galactosidase in E. coli

The effects of lactose, galactose, glucose, and glucose combined with galactose on the induction of β–galactosidase by IPTG in Escherichia coli strain VC10, growing in a glycerol media, were compared against a control of glycerol plus IPTG. After inducing β– galactosidase production with the IPTG, the cultures were altered with the addition of one of the above carbohydrates or combinations. This addition proved to alter the induction rate of the β–galactosidase, slowing it considerably in the case of glucose, lactose and the glucose combined with galactose. These results show some consistencies with the model of catabolite repression. The addition of galactose did not slow the β–galactosidase induction rate but instead seemed to provide an increase in this rate.