Mar 11, 2026
Preparing Antibiotics Stocks
This protocol is a draft, published without a DOI.
- Tamra Lahom1
- 1Carleton College
Protocol Citation: Tamra Lahom 2026. Preparing Antibiotics Stocks. protocols.io https://protocols.io/view/preparing-antibiotics-stocks-jv2dcn8a7
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: March 11, 2026
Last Modified: March 11, 2026
Protocol Integer ID: 313125
Keywords: preparing antibiotics stocks plasmid, antibiotics stocks plasmid, presence of an antibiotic resistance gene, more antibiotic resistance gene, antibiotic resistance gene, plasmid, specific antibiotic, antibiotic, bacteria in the presence, bacteria, resistance
Abstract
Plasmids can carry one or more antibiotic resistance genes, which confer resistance to a specific antibiotic to the bacteria carrying them. The presence of an antibiotic resistance gene on a plasmid allows researchers to easily isolate bacteria containing that plasmid from bacteria that do not contain it by artificial selection (i.e. growing the bacteria in the presence of the antibiotic).
Troubleshooting
Review Making Antibiotic Stocks
| A | B | C | |
| Antibiotic | Stock [M] | Working [M] | |
| Ampicillin | 100 mg/mL | 100 µg/mL | |
| Bleocin | 5 mg/mL | 5 µg/mL | |
| Carbenicillin* | 100 mg/mL | 100 µg/mL | |
| Chloramphenicol | 25 mg/mL (dissolve in EtOH) | 25 µg/mL | |
| Coumermycin | 25 mg/mL (dissolve in DMSO) | 25 µg/mL | |
| Gentamycin | 10 mg/mL | 10 µg/mL | |
| Kanamycin | 50 mg/mL | 50 µg/mL | |
| Spectinomycin | 50 mg/mL | 50 µg/mL | |
| Tetracycline | 10 mg/mL | 10 µg/mL |
Unless otherwise indicated, the antibiotic powder can be dissolved in dH2O.
*Carbenicillin can be used in place of ampicillin. Carbenicillin is more stable, so it is potentially more effective at selecting only bacteria containing the plasmids of interest (for example, fewer satellite colonies will grow). However, it is also more expensive.
Make the antibiotic
In a 15 mL falcon tube make the stock antibiotics. Make 10 mL at a time.
Aliquot 1mL of the antibiotics into 1.5 mL centrifuge tubes.
Label the tubes with the antibiotic and concentration.
Storage
Store in the antibiotics box in the -20 C freezer.