Posted 15 October 2004 - 09:17 AM
In my lab we save strains of bacteria by freezing them in 60% glycerol at -80 degrees C. When we need the bacteria again, we scoop out some of the frozen stock and put it in fresh liquid media. I don't know how common this practice is, but it has always worked fine for us. I have an E coli strain with a plasmid in it I am trying to save by freezing down as usual, but upon revival it doesn't seem to have the plasmid which is the whole reason I am saving the strain. The wierd part is that I already put this strain in the freezer and named it #266. We always make a second and often a third freezer copy in case the first one is lost or runs out. Strain #266 can be revived and contains plasmid, but every time I use the revived broth to make a new freezer culture the plasmid is lost.