I am using the QIAamp DNA Mini kit 250 from QiaGen for purify genomic DNA from E. coli. I have a biomass and I am looking for the best storage conditions because I am not going to perform the DNA extration immediatly. Can I freeze at -20 C E coli suspension for posterior extraction of DNA without affect its integrity and purity? There are other storage conditions better than this one?
I hope some help!! Thanks.
For short term storage you can store your bacteria cultures at +4C. For longer storage, centrifuge to collect a pellet bacteria prior to freezing.
There is a technique called "plasmid museum" when you amplify your target plasmid in E.coli and then mix a small amount of bacterial culture with glycerine and freeze the bacteria on -70. When you need the plasmid later, you may thaw this mix and grow a culture quickly for plasmid extraction, no need to repeat DNA ligation into vector, cell transformation and selection. I suppose that freezing in such manner preserves bacterial genomic DNA as well.
We didn't use special medium, just mixed liquid culture with glycerin. The culture should not be overgrown of course. (I suppose that when you need to thaw this suspension later you should do it slowly on ice to prevent cell damage, but I have never thawed plasmid museums myself).
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