Reference
Antibiotic reference
A reference for the antibiotics used to select transformed bacteria: stock and working concentrations, the solvent to dissolve them in, and how to store them. Working concentrations are the values commonly used for E. coli — always confirm against your plasmid and strain.
| Antibiotic | Stock | Solvent | Working (E. coli) | Storage | Notes |
|---|---|---|---|---|---|
| No antibiotic matches that search. | |||||
Working concentrations are the values commonly used for E. coli selection. The right concentration depends on your strain, plasmid copy number, medium and host — confirm against your plasmid map and the supplier before you rely on these. Concentrations for mammalian or yeast selection are entirely different.
Prepare stocks at the listed concentration in the listed solvent, filter-sterilise aqueous stocks, aliquot and store frozen. Add to medium only once it has cooled below about 55 °C, since heat destroys most of these antibiotics.
Frequently asked
Why does my plasmid resistance not match the plate?
The antibiotic must match the resistance gene the plasmid carries. Check the plasmid map for the marker, then pick the matching plate; a kanamycin plasmid will not grow on ampicillin.
Can I use ampicillin for a long incubation?
Ampicillin is degraded by the beta-lactamase the resistant cells secrete, so plates left too long grow satellite colonies around big ones. Carbenicillin is more stable, or pick colonies promptly.
Are these concentrations right for mammalian cells?
No. These are bacterial selection values. Mammalian selection uses different agents and concentrations, titrated per cell line with a kill curve, and is out of scope for this table.