I need to selectively isolate fungal cellulase/xylanase producers in a selective medium which supports both bacterial and fungal cellulase/xylanase producing organisms. Tetracycline, a broad spectrum antibiotic, has been shown to inhibit some fungal species. Sodium azide and cyclo-heximide can also prevent both bacterial and fungal growth. This condition is also applicable to some other common antibiotics. I need a more restrictive antibiotic with no known antifungal property so that I will not lose any chance of selecting the best fungal strain.
That is a difficult question! It is hard to say an antibiotic does not affect fungal development unless you tried it and furthermore the reaction will not be the same between different fungi. For growing our fungal strains on plate we use a combination of Streptomycin and Penicillin to prevent bacterial growth. But I am sure they will affect some fungi.
In the past we have also used Nalidixic acid as an antibiotic but maybe this is not strict enough for your purpose.
I am advice to keep your medium pH as acidic, this will be control all bacterial contaminants.
Thank you both for your response. @ Dr. Thangaswamy S., but we had got some acidophilic bacterial spp, Lactobacilli for example. I think as suggested by Dr Van Pelt,its better to try different antibiotics on the same soil sample independently and compare the fungal growth response.
To avoid bacterial growth you can use an antibiotic "cocktail". I used the following without problem and I could finally get rid of some annoying chloramphenicol-resistant bacteria (resisting 100mg/L) from my isolation cultures in PDA:
- 15 mg/L streptomycin sulfate
- 15 mg/L gentamicin sulfate
- 12 mg/L tetracycline hydrochloride
The good thing is that even if one of them is toxic for some fungi, the concentration is really low compared to the concentration you would need if you used only one antibiotic, e.g. chloramphenicol 100 mg/L
For resolve of this problem it's better that , you added tetracycline and ampicillin into medium .
streptomycin is good to stop fungus growth , I tried.. It should be added in traces..
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