storage of dental plaque samples - does -20 kill the bacterial plaque? (May/07/2006 )

hi every body
I have collected dental plaque samples for 15 days, dental plaque was suspended in PBS pH 7.5 and then were kept in - 20 freezer ????????
then I realized that this temperature may kill the bacteria in the plaque,
I need the bacteria to be alive for culture purposes.
i did a stupid thing I know. please advice me about this, Does this temperature kill the bacteria in the plaque samples? What is the suitable way to restore my plaque samples?

you'll get back the bacterias if you thaw in the fridge for 20-30'.
Also i've never done this, i sent you this advice bacause i know that some bacterias of my minipreps get well after a 4° thaw (freeze whithout glycerol)

You probably haven't killed all bacteria in your sample, so you will probably be able to culture something out of them. Now it depends on what you are looking for. If it's a few bacteria of different species, you will probably have enough survivors to get what you want. But if you wanted to sample diversity to get an idea of the population, you are in trouble. But then I would advise to culture as soon as sample are taken anyway.

But to store bacteria you increase the recovery if you add around 15% of glycerol before freezing.