One Shot BL21(DE3) Chemically Competent E. coli cells are ideal for use with bacteriophage T7 promoter-based expression systems such as pRSET and pET. This strain had been engineered to carry the λDE3 lysogen that contains T7 RNA polymerase gene under control of the lacUV5 promoter. Recombinant proteins that are nontoxic to E. coli are generally expressed at higher levels in BL21(DE3) cells compared to other strains with tighter expression control.

The BL21(DE3) E. coli strain is one of the most popular host strains to produce recombinant proteins and adapted in research or industrial applications. It is a derivative of the E. coli B strain that does not contain the lon protease and is also deficient in the outer membrane protease OmpT. The lack of two key proteases reduces degradation of heterologous proteins expressed in the strains. Additionally, several other strain features make them especially suited for protein production, namely fast growth in minimal medium, a lower acetate production when grown in high glucose media, and the ability to reach high cell density. One Shot BL21(DE3) Chemically Competent E. coli cells can achieve transformation efficiency of >1 x 10⁸ cfu/μg of control DNA.

Notes
• The basal expression levels of heterologous genes are significantly higher in BL21(DE3), thus strains such as BL21 AI are recommended for toxic protein expression.
• IPTG is required to induce expression of the T7 RNA polymerase cascade system that in turn transcribe T7 promoter regulated target gene.

One Shot BL21(DE3) Chemically Competent E. coli offer:
• Transformation efficiency of >1 x 10⁸ cfu/μg control plasmid DNA 
• Ion and OmpT protease deficiency reduces degradation of recombinant protein 
• IPTG-inducible lacUV5 promoter controls expression of the T7 RNA polymerase 
• hsdS mutation allows efficient transformation of unmethylated DNA 
• Fast growth in minimal medium and ability to reach high cell density

Easy-to-use One Shot format 
BL21(DE3) Chemically Competent E. coli cells are supplied in the convenient, single-reaction One Shot format. The single-tube, single-use format allows all steps of the transformation protocol, up to plating, to take place in the same tube, thereby helping save time and prevent contamination.

Genotype: F–ompT hsdSB (rB–, mB–) gal dcm (DE3)

Find the strain and format that you need
We offer other E. coli strains for protein expression. For expression of toxic proteins, consider BL21-AI™ One Shot™ Chemically Competent E. coli.
BL21 Star (DE3) and other strains are available in MultiShot formats for high throughput applications.
Explore bacterial growth media formats.
We offer a variety of systems for the expression of recombinant proteins in E. coli. The Champion pET expression system provides the highest level of protein production available in any expression system.