FAQ: Is T7 expression subject to catabolite repression in NEB T7 Express or SHuffle strains?

The T7 RNA polymerase gene is cloned into the chromosomal lac operon. Since expression is controlled by the wt lac operon, glucose addition will result in catabolite repression. Thus, basal protein expression from T7 promoter vectors will be better controlled when glucose is present in the media.

When glycerol is the primary carbon source, there should no effect on the lac operon.