Please let me know, what is difference between BL21 (DE3) and BL21 (CDE3)?

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Dominique Liger

Hi there,

I guess C in CDE3 stands for CodonPlus which means the strain is bearing a plasmid confering resistance to Chloraphenicol and encoding for some rare tRNAs in order to improve translation efficiency. For more info:

https://www.agilent.com/cs/library/usermanuals/public/230240.pdf

Sehee Lee

Thanks, I think this strain is very old or rarely used. Or maybe the record is wrong. Thank you again for the information you gave me.

Wiwiek Harsonowati

Note that BL21 does not carry the gene for T7 RNA polymerase and thus is only suitable for expression from promoters recognized by the E.coli RNA polymerase: e.g. lac, tac, trc, ParaBAD, PrhaBAD and also the T5 promoter.

BL21 (DEG3) carries the gene for T7 RNA polymerase under control of the lacUV5 promoter

but I don‘t know for CDEG.... I think it’s very rare