Some interesting result from pLac-RFP
Motivation:
we want the low copy plasmid backbone pSB4A5, and we know that the strain JM 109 has lacQ on its F plasmid. We wonder if the lacI expressed from F plasmid can repress the pLac on the pSB4A5.
Parts:
J04450 (backbone is pSB4A5)
Resource:
J04450: from Lin Min, Plasmid
2009.8.13
Transformation:
Plasmid J04450, competent cells JM109 100uL,
Smear to LB plate with Amp
2009.8.14
The colonies on the plate became a little red, after 24 hours.
But compare to no RFP colonies, they are just a little brighter.
The second picture is for comparison with no GFP colonies.
2009.8.16
Inducing:
Transfer one colony into 5mL LB, when it grows to OD 0.4~0.6. Add some IPTG (1mM) to induce, and half without any IPTG, as a control.
After 4 hours, the difference is obvious:
The left one is control, the right one is induced.
Result & discussion
The result suggests that we can make use of the lacIQ on the F plasmid of JM 109, if the pLac is on a low copy plasmid (such as pSB4A5, copy number=5). The amount of lacI can largely repress the expression of pLac. So, maybe we can construct the AND gate only use pLac, without any other lacI on that plasmid.
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