Simplifying Strain Selection
CONSIDERATIONS FOR CHOOSING THE BEST E. COLI STRAIN FOR ANY APPLICATION
They’re everywhere: our bodies, our environments, and of course, our laboratories. Escherichia coli is the most well-known bacterial species and has become an irreplaceable tool in the molecular biology field. There are hundreds, if not thousands, of different E. coli strains used in scientific research, each with their own unique modifications. This can make choosing the correct strain for your research a daunting task. The guidelines below can simplify this process and help you choose the best strain for your application.
Laboratory E. coli strains used in molecular cloning can typically be classified as either expression strains or propagation strains. If you need to amplify and extract a particular plasmid or construct, it is best to use a propagation strain. On the other hand, if your goal is to express a protein encoded within a plasmid, an expression strain is the best choice. While there are many details involved in choosing a strain, the table below provides an overview of the most common laboratory strains and their key features.
|
Strain |
Propagation or |
Antibiotic |
When to Use? |
|---|---|---|---|
|
DH5α |
Propagation |
N/A |
General Cloning and |
|
JM109 |
Propagation |
N/A |
General Cloning and |
|
HB101 |
Propagation |
Streptomycin |
Good for |
|
Zymo 10B |
Propagation |
Streptomycin |
General Cloning and |
|
TG1 |
Propagation |
N/A |
General Cloning and |
|
NEB Stable |
Propagation |
N/A |
Good for Lentivirus |
|
XL1 Blue |
Propagation |
Tetracycline |
Blue/White Screening |
|
XL10 Gold |
Propagation |
Tetracycline and |
Large Plasmid |
|
BL21 (DE3) |
Expression |
N/A |
General Protein |
|
BL21 (DE3) pLysS |
Expression |
Chloramphenicol |
Toxic Protein |
|
Lemo21 (DE3) |
Expression |
Chloramphenicol |
Insoluble/Membrane |
|
T7 Express |
Expression |
N/A |
General Protein |
|
BLR (DE3) |
Expression |
Tetracycline |
Unstable Protein |
|
XJa (DE3) Autolysis |
Expression |
Chloramphenicol |
Recombinant Protein |
|
XJb (DE3) Autolysis |
Expression |
Chloramphenicol |
Recombinant Protein |
It is important to have a defined research goal when choosing an E. coli strain. Are you aiming to clone highly repetitive or large plasmids? If so, use a specialized strain that can maintain high transformation efficiency. Are you aiming to express a toxic protein? If so, choose a strain that has been designed to withstand toxic environments.
Both propagation and expression strains carry specialized mutations that allow them to thrive under specific conditions and it is important to keep these features in mind when choosing the right strain for your project. Mix & Go! Competent Cells are a great choice for propagation, as they enable high transformation efficiencies in just 20 seconds. If you are in search of an expression strain, XJ Autolysis Competent Cells can simplify the process with an efficient, gentle lysis system. No matter the application, Zymo Research scientists are available to assist you with your strain selection process.
