As the title suggests, I am not entirely sure how to prepare my plates for blue-white colony screening. I understand that I need agar plates without glucose for this type of screening to work, however I do not know whether the plates that we usually use are prepared with glucose or not (I suspect they are) and the kitchen staff that prepares the plates do not know either. So my questions are: Are standard plates for bacterial spreading usually prepared with glucose? I know our staff uses Bacto Tryptone BD and Bacto yeast extract, does anyone have an experience with these and know whether they contain glucose?
Normally rich media like LB do not have glucose added. However I wouldn't worry too much about it, the sensitivity of XGAL is high enough that even with glucose present you will still see blue colonies. Glucose mediated catabolite repression is only partial and not complete.
I will try it with our standard plates then. Thank you very much Michael.
If it is for the cloning you need prepare: 0,7 gr Tryptone, 0,35 gr Yeast, 0,35 gr NaCl, 1,05 gr Agar for 70 ml of ddH2O. After I add 70 µl Amp, 350 µl IPTG and 70 µl X-Gal (1 ml Amp, 5 ml IPTG, 1 ml X-Gal for 1 ml of medium).
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