If you've just frozen them down for future RNA analysis (i.e. you don't care if they retain any viability) then I would store them at -80. RNA is...not the world's most stable molecule, and does degrade slowly (but steadily) when stored at -20. Ok, it degrades slowly but steadily at -80, too, but orders of magnitude more slowly.

Basically, always store RNA at -80.

If you haven't frozen them down yet, resuspend them in TRIzol first, then freeze at -80. Cells dissolved in TRIzol (and then frozen) will give better quality RNA than cells frozen (and then defrosted and dissolved in TRIzol).

Bacterial cells can be stored at -20°C using a 40-50% glycerol solution. You can revive the cells by culturing the stored sample in LB medium at any point and extract RNA or use it for any other purpose..

Hope I got your question right..

If you've just frozen them down for future RNA analysis (i.e. you don't care if they retain any viability) then I would store them at -80. RNA is...not the world's most stable molecule, and does degrade slowly (but steadily) when stored at -20. Ok, it degrades slowly but steadily at -80, too, but orders of magnitude more slowly.

Basically, always store RNA at -80.

If you haven't frozen them down yet, resuspend them in TRIzol first, then freeze at -80. Cells dissolved in TRIzol (and then frozen) will give better quality RNA than cells frozen (and then defrosted and dissolved in TRIzol).

I agree with Mr. John. TRIzol would be a better reagent to store.

• You can also use guanidine solution (contains RNase inhibitors) for storage followed by TRIzol extraction.
• RNALater reagent is also a very good option.

Good luck!