Gene Expression of the lac operon using IPTG
To show how genes can be regulated by using the lac operon as an example.
BL21 (DE3) + egfp (un-induced)
3 agar plates with Kanamycin
0.5 mM IPTG
Plate 2 kanamycin plates with un-induced BL21(DE3) + egfp.
Label plates no IPTG and IPTG
Place in 37°C incubator overnight
To turn gene on for expression
Plate 1: Do not add anything
Plate 2: Using a sterile pipette tip, add 8 µL 0.5 mM IPTG per colony.
Allow IPTG to soak in
Incubate at 37°C overnight
Place the plate under UV light to see bacteria glow.
**Calculation: To make 0.5 mM IPTG, mix 50 µL 1.0 M IPTG + 50 µL LB broth
**I was also going to do a third plate with lactose to see if this would make the bacteria glow
since lactose will express the lac operon. However, we did not have any lactose. This would be
a cool extension of this lab that might be more relatable to the students.
Lab by Ingrid Coulson,
9th grade Honors Biology teacher
Broughton High School, Raleigh, NC