A Peculiar Event In Tranformation

Paul Dunman dunman at njmsa.UMDNJ.EDU
Wed Jun 18 16:41:04 EST 1997


Randy Willis <willis at gandalf.psf.sickkids.on.ca> writes:

>Paul N Hengen wrote:
>> But, will they be able to grow under non-selective conditions? I think the
>> cells undergo more stress (not less) at 4C. I used to keep all my slants of
>> E. coli at 4C until I found out they last much longer if stored at room temp.
>> Then again, who needs the cells when you're studying plasmids?  I now just
>> make sure to keep any plasmid DNA I'm interested in at -20C.


>Paul,

>You may be correct.  My use of the word "stress" is very hand-waving.  I
>do agree that it is best to keep a solution of DNA at -20C, and I do.  I
>wonder what peoples' experiences have been with using cells taken from
>stocks which have been frozen at -70C.  We maintain stocks, but
>typically this is in case we run out of plasmid DNA and NOT for the
>purposes of growths/expressions.  Any suggestions or ideas?

>Best of luck to all in their endeavours...Randy


Our lab typically stores all strains at -20C & -70C in 40% gylcerol.  
I've had trouble recessitating (sp) strains from -20C after they've been 
stored for several years.  However, I've never had trouble recessitating 
strains from -70C.  I directly plate on selective media & "knock on wood" 
haven't ran into a problem yet.  I should also mention, all plasmids are 
also purified & stored @ -20C...just in case.

Paul D.




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