Genotypes of Invitrogen™ competent cells

Product Name Genotype


F– mcrA Δ(mrr-hsdRMS-mcrBC) Φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara leu) 7697 galU galK rpsL nupG λ–

DH10B™ T1R

F– mcrA Δ(mrr-hsdRMS-mcrBC) Φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara leu) 7697 galU galK rpsL nupG λ– tonA


F– mcrA Δ(mrr-hsdRMS-mcrBC) Φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara leu) 7697 galU galK λ– rpsL nupG/ pMON14272/pMON7124

MegaX DH10B™ T1R

F– mcrA Δ(mrr-hsdRMS-mcrBC) Φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara leu)7697 galU galK λ– rpsL nupG tonA

Genotype Key

Genotype Description


Blocks arabinose catabolism 


Ornithine carbamoyltransferase mutation blocks ability to use arginine 


Abolishes endogenous adenine methylation at GATC sequences (dam) or cytosine methylation at CCWGG sequences (dcm). Used to propagate DNA for cleavage with certain restriction enzymes (e.g. Ava II, Bcl I) 


Lysogen that encodes T7 RNA polymerase. Used to induce expression in T7-driven expression systems 


endA Mutation in the non-specific endonuclease Endonuclease I; eliminates non-specific endonuclease activity, resulting in improved plasmid preps 


A self-transmissible, low-copy plasmid used for the generation of single-stranded DNA when infected with M13 phage; may contain a resistance marker to allow maintenance and will often carry the lacI and lacZ∆M15 genotypes 


Galactokinase mutation blocks catabolism of galactose—cells that are galK minus grow in the presence of galactose as the sole carbon source 


Glucose-1-phosphate uridylyltransferase mutation blocks ability to use galactose—cells that are galU minus can grow on media that contains galactose as the sole carbon source 


DNA gyrase mutant produces resistance to nalidixic acid 


Mutations in the system of methylation and restriction that allow E. coli to recognize DNA as foreign. The hsd genotype allows efficient transformation of DNA generated from PCR reactions *hsdR–eliminates restriction of unmethylated EcoK I sites. (1) **hs 


Encodes the lac repressor that controls expression from promoters that carry the lac operator; IPTG binds the lac repressor and derepresses the promoter; often used when performing blue/white screening or to control expression of recombinant genes 


Blocks use of lactose via β-D-galactosidase mutant 


β-D-galactosidase gene; mutations yield colorless (vs. blue) colonies in the presence of X-gal 


Element required for β-galactosidase complementation when plated on X-gal; used in blue/white screening of recombinants; usually carried on the lambdoid prophage φ80 or F´ 


Requires leucine for growth on minimal media via β-isopropyl malate dehydrogenase mutation 


lon Deficiency in the Lon ATPase-dependent protease; decreases the degradation of recombinant proteins; all B strains carry this mutation 

mcrA, mcrBC,or mrr 

Mutations that allow methylated DNA to not be recognized as foreign; this genotype is necessary when cloning genomic DNA or methylated cDNA  


Mutation for the transport of nucleosides 


Indicates that the E. coli lack an outer membrane protease—reduces degradation of heterologous the strains and recovery of intact recombinant proteins is improved in ompT minus strains 


A 60-kb low-copy plasmid that carries the ampicillin and tetracycline resistance genes with amber mutations; used predominantly for selection of supF-containing plasmids; carries the kanamycin resistance gene for selection 


pLys Plasmid that encodes T7 lysozyme; used to reduce basal expression in T7-driven expression systems by inhibiting basal levels of T7 RNA polymerase 


proAB Requires proline for growth on minimal media 


Mutation in a gene responsible for general recombination of DNA; particularly desirable when cloning genes with direct repeats 


RNA is synthesized in absence of protein synthesis (relaxed phenotype) relA locus regulates the coupling between transcription and translation. In the wild type, limiting amino acid concentrations results in the shutdown of RNA synthesis (also known as th 


Confers resistance to streptomycin (this makes a mutant ribosomal protein, small subunit, the target of the drug) 


tRNA glutamine suppressor of amber (supE)(UAG) or tyrosine (supF) 


Requires thiamine for growth on minimal media 


Confers tetracycline resistance via a transposon 


Confers resistance to the lytic bacteriophage T1, T5 and f80 

traD, D36  

Prevents transfer of F' episome via transfer factor mutation 


Confers resistance to phage T6 and colicin K 


Blocks catabolism of xylose