Antibiotic stocks and working concentrations

The following antibiotics can be used for selection at these concentrations in most Streptomyces sp. (If working with a new species, you should always first check whether it has intrinsic resistance to an antibiotic before attempting to use it.)

Antibiotic	Stock [mg/ml]	Final concentration [µg /ml]
Apramycin	100 in dH2O	50
Hygromycin	50 in dH2O	100
Kanamycin	50 in dH2O	50
Chloramphenicol	25 in 100% EtOH	25
Carbenicillin	100 in dH2O	100
Thiostrepton	50 in 100% DMSO	50
Nalidixic acid	25 in 0.2N NaOH	25

Notes:

• Hygromycin selection is salt-sensitive; on low-salt media such as DNA, 50 µg /ml (final concentration) is sufficient for selection.
• Carbenicillin is more stable than ampicillin, but care should still be taken to avoid excessive freeze/thaw cycles which could result in degradation of the antibiotic.