E. coli strains

Jens Alfken alfken at zedat.fu-berlin.de
Mon Aug 25 11:07:52 EST 1997

> Stratagene has designed some E. coli strains for specific purposes such as
> "ABLE" for difficult cloning, "SURE" for unstable DNA and "TOPP" for
> difficult protein expression. Before investing in buying such strains, I
> would be interested in knowing if any of you ever used them and if it
> worked fine or not.

I«ve been using the SURE strain. I work with Z-DNA and Stratagene says
that Z-DNA is more stable in SURE strain e.coli. The one instance where
I could compare SURE to DH1alpha was when making a plasmid library with
the synthetic insert (YR)8 (Y=pyrimidine, R=purine). Using DH5alpha I
got a lot of jumbled sequences, most likely due to recombination. With
SURE this problem was much less prevalent. However I got quite a number
of dinucleotide deletions typical for what E.coli can do to Z-DNA. Ah,
and I should include a caveat that I«ve never proven that the problems
arose in the backies and are not due to some other cloning related
problem. Once inside the bacteria the sequences appeared to be quite
stable in both DH5alpha and SURE. 
In Summary : Yes, there are differences between the strains but don«t
expect miracles.

Jens Alfken

Institut fŸr Molekularbiologie und Biochemie
FU Berlin

alfken at zedat.fu-berlin.de

More information about the Methods mailing list