Disappearing plasmids

[Arthur Wohlwill]

In article <50dk6r$a1u at flood.weeg.uiowa.edu> cmstoltz at vaxa.weeg.uiowa.edu (Marty Stoltzfus) writes:
>From: cmstoltz at vaxa.weeg.uiowa.edu (Marty Stoltzfus)
>Subject: Disappearing plasmids
>Date: 2 Sep 1996 03:27:23 GMT

>Off and on our laboratory has experienced an annoying problem only with
>pUC vector clones but never with other high copy plamids such as 
>Bluescript or low copy plasmids with the same size inserts.  When we
>screen our minipreps, we have high amounts of plasmid DNA (bact. strain is
>HB101 in LB + 200 mic./ml AMP). Then when we grow up maxipreps we find
>that sometimes even though the bacteria grow normally in AMP we have lost
>most or all the plasmid.  This happens even though we have streaked for
>single colony isolation.  Why is this happening?  We would appreciate
>any help we can get to solve this frustrating problem.
>        Marty Stoltzfus


I have had problems with HB101 large preps that had to do with  Dnase's.  Like 
you, I had no problems with minipreps, but did have problems with larger scale 
preps.  The problems went away when I added a proteinase K step to my 
protocol.  I cant recall whether I had problems with some vectors and not 
others--It was over 10 years ago.  Good luck,
Arthur Wohlwill Adwohlwi at UIC.EDU