IPTG uptake by E. coli can be independent of the action of lactose permease, since other transport pathways are also involved.

It is significantly less stable in solution; Sigma recommends storage for no more than a month at room temperature.

Typically, a sterile, filtered 1 mol/L solution of IPTG is added 1:1000 to an exponentially growing bacterial culture, to give a final concentration of 1 mmol/L.

If lacIq, a mutant that over-produces the lac repressor, is present, then a higher concentration of IPTG may be necessary.

Blue-white screen allows colonies that have been transformed with the recombinant plasmid rather than a non-recombinant one to be identified in cloning experiments.