Genotypes of Invitrogen™ competent cells

Product Name Genotype

DH5α™

F– Φ80lacZΔM15 Δ(lacZYA-argF) U169 recA1 endA1 hsdR17 (rK–, mK+) phoA supE44 λ– thi-1 gyrA96 relA1

DH5α™ T1R

F– Φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17 (rK–, mK+) phoA supE44 thi-1 gyrA96 relA1 tonA

Genotype Key

Genotype Description

ara-14 

Blocks arabinose catabolism 

argF 

Ornithine carbamoyltransferase mutation blocks ability to use arginine 

dam/dcm 

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) 

DE3 

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

endA 

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

F´  

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 

galK 

Galactokinase mutation blocks catabolism of galactose—cells that are galK minus cannot grow in the presence of galactose as the sole carbon source 

galU 

Glucose-1-phosphate uridylyltransferase mutation blocks ability to use galactose—cells that are galU minus cannot grow on media that contains galactose as the sole carbon source 

gyrA96  

DNA gyrase mutant produces resistance to nalidixic acid 

hsd  

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 

lacI  

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 

lacY1  

Blocks use of lactose via β-D-galactosidase mutant 

lacZ  

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

lacZ∆M15  

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´ 

leuB  

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

lon  

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  

nupG  

Mutation for the transport of nucleosides 

ompT  

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 

P3  

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  

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  

proAB Requires proline for growth on minimal media 

recA  

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

relA  

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 

rpsL 

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

supE,F 

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

thi-1  

Requires thiamine for growth on minimal media 

Tn10  

Confers tetracycline resistance via a transposon 

tonA 

Confers resistance to the lytic bacteriophage T1, T5 and f80 

traD, D36  

Prevents transfer of F' episome via transfer factor mutation 

tsx  

Confers resistance to phage T6 and colicin K 

xyl-5  

Blocks catabolism of xylose