Contaminating plasmid

Patricia Foster pfoster at
Thu Jan 13 18:44:53 EST 1994

 > A number of us have had problems with a plasmid which seems to
: > contaminate our plasmid stocks. It's ampicillin resistant and
: > has a linear size of around 2.2 kb. The strangest aspect is the
: > lack of sites for common restriction enzymes. It has an SstI (SacI)
: > site but lacks sites for BamHI, HindIII, KpnI, PstI, EcoRI, SalI
: > and EcoRV.
X-Newsreader: TIN [version 1.2 PL0]

   Me too!  Since it is in pUC preps, can't be due to the f1 origin.  I would
bet that it is some recombination product that coli is making at a low 
frequency all the time, but occasionally it gets replicated up to high
frequency (i.e. if the product contains the AmpR, or the proper origin).
  E. coli is a marvelously inventive creature.
Patricia L. Foster
Boston University School of Medicine
Boston, MA USA
pfoster at

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