One Shot™ BL21-AI™ Chemically Competent E. coli (Invitrogen™)

One Shot BL21-AI Chemically Competent E. coli cells are designed for applications that require tight regulation and strong expression of toxic proteins from any T7-promoter-based expression systems. A derivative of the E. coli B strain, BL21-AI does not contain the lon protease and is deliberately deficient in the outer membrane protease OmpT.

The lack of two key proteases reduces degradation of heterologous proteins expressed in the strain. Additionally, several other strain features make these cells especially well 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.

BL21-AI E. coli contain a chromosomal insertion of a cassette containing the T7 RNA polymerase (T7RNAP) into the araB locus of the araBAD operon, placing regulation of T7 RNAP under the control of the arabinose-inducible araBAD promoter. The araB gene is deleted in this strain. The presence of the tetA gene confers resistance to tetracycline and permits verification of strain identity using tetracycline. The yield of recombinant protein obtained from BL21-AI is generally similar to that obtained from BL21 (DE3). BL21-AI, due it’s qualities and genomic background, was used to elucidate fundamental steps in the adaptation process of the CRISPR/Cas system. One Shot BL21-AI Chemically Competent cells have a transformation efficiency of >1 x 10⁸ cfu/μg plasmid DNA.

One Shot BL21-AI Chemically Competent E. coli offer:
• Transformation efficiency of >1 x 10⁸ cfu/μg control plasmid DNA
• Ion and OmpT protease deficiency that reduces degradation of recombinant protein
• T7 RNA polymerase controlled by the tightly regulated arabinose-inducible araBAD promoter
• hsdS mutation that allows efficient transformation of unmethylated DNA
• Ideal for inducing expression of toxic protein from any T7 promoter-based plasmid

Easy-to-use One Shot format
BL21-AI 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 hsdS_B (r_B^–, m_B^–) gal dcm araB::T7RNAP-tetA

Find the strain and format that fits your needs
We offer several E. coli strains for protein expression.
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.

Notes
• To induce expression from the araBAD promoter, use L-arabinose. To repress basal expression from the araBAD promoter, use glucose. Even if glucose is absent, basal expression from is generally low.
• BL21-AI strain genome sequences available in the NCBI GenBank database under accession number CP047231 (Bhawsinghka et al. 2020).