Antibiotics

Writing/Editing Credit: Mark Mandel, Tiffany Lowe-Power

Preparation of 1000x stocks

Prepare 20 mL at a time and aliquot

Antibiotic	Color	Abbr	Concentration (mg/mL)	Solvent	Stock notes
Kanamycin	PURPLE	Kan	25	dH20	Filter
Gentamicin	BROWN	Gm	10	dH20	Filter
Spectinomycin	BLACK	Sp	40	dH20	Filter
Tetracycline	GREEN	Tet	10	75% ethanol	Filter; Keep dark (foil wrap)
Ampicillin	RED	Amp	100	dH20	Filter
Chloramphenicol	YELLOW	Cam	25	95% ethanol	Filter

Note that the dry gentimicin is stored at room temperature and dry tetracycline is stored at -20 °C, but most dry antibiotics are stored at 4 °C.

For each stock aliquot approximately 1.2 mL per 1.5 mL tube and store in antibiotics racks at -20 °C. Label with colored stripe on lid and concentration (e.g. “50” for 50 mg/mL).

Tetracycline is in the red light sensitive box, and is aliquoted in 500 μL and 50 μL volumes because each aliquot is single use and excess should be discarded.

Note that there is additional information about making antibiotic-containing media listed under media.

“Filter” refers to filter sterilizing with 0.22 μm filters.

Working concentrations for E. coli and Ralstonia

These stocks are at 1000x concentration, so add 1/1000th volume for regular use (e.g. 500 μL to 500 mL medium). If selecting in a minimal medium, a lower antibiotic concentration may be necessary.