Berglund:Cells Available

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Berglund Lab Competent Cells

Competent Cells
Strain Company Cloning Protein House Bought Singles Antibiotic
NovaBlue Novagen X X X X
TG1 Zymo Research (?) X X
TOP10 Invitrogen X X X
BL21(DE3) Novagen X X X
BL21(DE3)pLysS Novagen X X X X Cam
BL21 Star Invitrogen X X
Rosetta(DE3) Novagen X X X Cam



General cloning cells. High transformation efficiency, blue-white screening capability. K-12 strain. Best for general day-to-day cloning and plasmid preps.

  • Note: According to product information from Novagen, this strain has tetracycline resistance. We've never applied this selection, so it's possible that TetR has been lost in our house cells. Something to keep in mind if using a TetR plasmid.


General cloning cells that grow FAST. High transformation efficiency, blue-white screening capability. Can be used to transform in the morning and obtain colonies in the evening. WARNING: be careful not to grow overnights too long, or your miniprep yield may be low. Originally received from Prehoda lab, so source is unclear.


Cloning cells received with TOPO cloning kits. High transformation efficiency, blue white screening capability. Similar to DH10B strain.


Standard protein expression strain. Deficient in a few proteases. The DE3 lysogen (an inactive phage genome integrated into the bacteria's genome) contains IPTG-inducible T7 RNA polymerase for inducing protein expression using the lac promoter. The pLysS plasmid encodes T7 lysozyme, a natural inhibitor of T7 RNApol, which represses basal/leaky expression. Strains with pLysS require chloramphenicol (Cam).

BL21 Star

BL21 derivative that contains a truncated RNaseE enzyme which increases mRNA stability (and supposedly increases protein yield).

  • Kristy prefers these over "plain" BL21 cells because they seem to grow faster.


BL21 derivative designed to enhance expression of proteins with rare codons. Contains an extra plasmid (pRARE) with tRNAs uncommon in E.coli, so always needs Cam selection.

  • Try these if having trouble with other strains. These are only bought and are somewhat pricey.