- The principle is that X-Gal (5-bromo-4-chloro-3-indolyl-b-D-galactopyranoside) turns blue when reacts with beta-galactosidase.
- Mix 20 ul X-Gal 20 mg/ml and 80 ul SOC and spread on LB+amp plates (X-Gal and DMF are toxic, use face-mask for your safety!!! X-Gal is light-sensitive, remember to keep it in the dark, when possible)
- Incubate with 200 ul bacteria
- Result: blue colonies express LacZ, while white colonies don't.
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40 mg/ml X-gal in DMF
SOC medium
Pre-warmed LB agar plate
Face mask
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