Antibiotic stocks and working concentrations

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The following antibiotics can be used for selection at these concentrations in many 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. Generally speaking, apramycin and hygromycin are likely to be more useful as selective markers than e.g. kanamycin and carbenicillin.)

Antibiotic Stock [mg/ml] Final concentration [µg /ml]
Apramycin 100 in dH2O 50
Carbenicillin1 100 in dH2O 100
Chloramphenicol 25 in 100% EtOH 25
Cycloheximide2 25 in 100% EtOH 25
Hygromycin3 50 in dH2O 100
Kanamycin 50 in dH2O 50
Nalidixic acid 25 in 0.2N NaOH 25
Thiostrepton 50 in 100% DMSO 50


1Carbenicillin 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.

2Cycloheximide is toxic, prepare the solution in a fume hood and take care when handling

3Hygromycin selection is salt-sensitive; on low-salt media such as DNA, 50 µg /ml (final concentration) is sufficient for selection.