---+ Commonly Used <em>E. coli </em>Strains <a target="_blank" href="https://openwetware.org/wiki/E._coli_genotypes">OpenWetWare</a> offers a comprehensive repository of the genotypes of the most commonly used<em> E. coli </em>strains. The following table points out some important features to take into account when working with some these _E. coli_ strains. | *Strain* | *Genotype* | *Observations* | | _E. coli_ DH5α | F<sup>–</sup> _endA1_ _glnV44_ __thi-1__ _recA1_ _relA1_ _gyrA96_ _deoR_ _nupG_ _purB20_ φ80d<em>lacZ</em>ΔM15 Δ( _lacZYA-argF_)U169, hsdR17(<em>r<sub>K</sub></em><sup>–</sup><em>m<sub>K</sub></em><sup>+</sup>), λ<sup>–</sup> | This strain is *auxotrophic for thiamine* ( _thi-1_) so that *requires supplementation* to be grown in minimal media such as DM. It has been observed that in minimum medium, even supplemented with thiamine (i.e. M9), this strain *grows slowly* compared to other strains such as BL21 and BW25113. | | _E. coli_ TOP10 | F- mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 nupG recA1 araD139 Δ(ara-leu)7697 galE15 galK16 rpsL(Str<sup>R</sup>) endA1 λ<sup>-</sup> | | | _E. coli_ BL21 | F<sup>–</sup> _ompT_ _gal_ _dcm_ _lon_ <em>hsdS<sub>B</sub></em>(<em>r<sub>B</sub></em><sup>–</sup><em>m<sub>B</sub></em><sup>–</sup>) [<em>malB</em><sup>+</sup>]<sub>K-12</sub>(λ<sup>S</sup>) | BL21 is a B strain of _E. coli_, somewhat related to REL606. BL21 is protease deficient, which makes it an excellent strain for protein expression. It has much faster growth compared to cloning strains. Some labs do use BL21 for maintaining plasmids, but it is not ideal due to the presence of nuclease and the fact that the strain contains recA. BL21 (DE3) is an engineered variant of BL21 which contains T7 RNA polymerase controlled by the lac operator, commonly used for expression of large amounts of burdensome or toxic proteins. | | _E. coli_ BW25113 | <p><em>lacI</em><sup>+</sup><em>rrnB</em><sub>T14</sub> Δ<em>lacZ</em><sub>WJ16</sub> <em>hsdR</em>514 Δ<em>araBAD</em><sub>AH33</sub> Δ<em>rhaBAD</em><sub>LD78</sub> _rph-1_ <br />Δ<em>(araB–D)567</em> Δ<em>(rhaD–B)568</em> Δ<em>lacZ4787</em>(::<em>rrnB-3</em>) _hsdR514_ _rph-1_ </p> | | -- Main.CamiloGomez - 14 Dec 2017
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Topic revision: r2 - 2024-07-09 - TylerDeJong