3 replies to this topic

[Ziv]

Hi all,

 

I've just started growing yeasts ( Candida Albicans) and have a question regarding their selective agar:

 

I'm using a standard Oxide Yeast extract agar that requires the addion of Tetracyclin for selection.

 

I read online that Tetracyclin melting temperatue is 141 c, does that mean I can use the Pour plate method instead of making petri dish alll the time? meaning I can solidify and melt the agar(with the anytibiotic added) multiple times?

 

Thanks in advance

 

Ziv

[bob1]

No - melting temperature does not equate to stability. Tetracycline is particularly unstable in aqueous solution, it will last a few days.

 

You can find information about stability from most suppliers - it should be on the data-sheet.

 

Here's one such sheet I found and the relevant information, note the 3rd sentence (bolded by me):

 

 

Tetracycline hydrochloride is stable if stored in a dry place and protected from light. It is water-soluble with approx. 11 mg/ml at 28°C. The stability in solutions is optimal at pH 3 - 5.2 (shelf life approx. 6 - 12 days). It may be stored between -20°C and 37°C. Since Tetracyclin is light-sensitive, solutions and agar plates containing TC should be protected from light. The recommended working concentration is 10 - 50 μg/ml, the stock solution e.g. 1.25 mg/ml. Magnesium ions antagonize with the activity of TC.

[Ziv]

I of course ment degredation temperatue, thank you for your answer!

[bob1]

Degradation and melting are two different things - in solution tetracycline will degrade quite quickly in the absence of heating. As far as I know, you can not heat tetracycline in solution and expect it to work after heating.

 

Now, I have no idea if you could heat the crystalline form to melting point and if it will stay stable after that, but I suspect it would not work as well as it would before melting.