Dear Waqar, we prefer to store bacterial stocks in 20% (v/v) final glycerol concentration and after growing them in broth. We do not use 0.85% NaCl. Directly mix growing culture with 40% glycerol in 1:1 ratio. It is our choice.
Best regards.
Dear Waqar
0,85% of NaCl is roughly 150mM which is required to maintain the osmotic balance and then the physiological shape of bacteria in solution.
As already mentioned by Mert it is not required for storage and 15-20% glycerol is sufficient. Just a suggestion: when you want to use the stock do not freeze/thaw but scrape the top of the tube and inoculate. this will keep your stock functional almost forever.
Best,
Edoardo.
I second Edoardo - to keep the osmotic balance in checks...for many sorts of commonly used bacteria this NaCl concentration is ideal ionic strength.
If You want to store bacterial culture for a weeks or 2 (-4 ), and want to reuse and require to maintain the CFU then? if we need to add glycerol or only take out the media and replace with equal volume of Normal saline or PBS is ok?
Dear waker
the main role of .85% of NaCl prevent from osmotic stress.
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