E.coli strain

Michael Benedik benedik at uh.edu
Wed Nov 20 10:27:42 EST 1996

In article <56umed$2it at scotsman.ed.ac.uk>
chrisb at hgu.mrc.ac.uk (Chris Boyd) writes:

> Dave Smith (davesmith at bioch.tamu.edu) wrote:
> : Thomas Broschard <Thomas.Broschard at esbs.u-strasbg.fr> wrote:
> : >Does anyone have the E. coli K12 strain KK2186.  This strain is 
> : >genetically identical to JM103 except that it is nonlysogenic for 
> : >bacteriophage P1.  The strain has originally been described by Berman 
> : >and Zagursky in a paper in Gene (1984) 27: 183-191 and is mentioned in 
> : >Jeffrey Millers's Handbook 'A short course in bacterial genetics'.  
> : >Please let me know at the e.mail address janel at esbs.u-strasbg.fr.
> : >Thank you in advance.  Regine Janel
> : We discovered JM103 was a P1 lysogen about five years ago--everyone
> : has to reinvent a wheel sometime in their life.
> : We cured the strain and now call it JM103Y.  If you are interested in
> : it, let me know and I'll see if we can send it your way.
> I can't understand why anyone would choose to use JM103 as a cloning
> host these days, whether cured of its P1 or not, primarily because it's
> recA+ and rk+ mk+. This means it's poor for cloning heterologous DNA
> (which is liable to EcoK restriction) and poor at maintaining repeated
> sequences (recombination proficient). You could use JM109, which is
> very similar to JM103 (-P1) except that it is recA- and rk-.
> However, for maximal transformation efficiencies, I would recommend
> DH11S for M13 work and DH10B otherwise. Both are available from
> GibcoBRL (no connection, other than a rather peevish niggle about them
> not replying to strain requests from me).
> Best wishes,
> --
> Chris Boyd                       | from, | MRC Human Genetics Unit
> chrisb at hgu.mrc.ac.uk             |  not  |  Western General Hospital
> http://www.hgu.mrc.ac.uk/~chrisb |   for |   Edinburgh EH4 2XU, SCOTLAND

JM103 is R-M+ (you are thinking of JM101 which is R+M+). The genetic
background of JM103 is different than JM109, people shouldn't think
that all the JM strains come from the same background. They don't. They
have different properties. I like using a recA+ strain because the
cells survive much much longer on petri dishes in the frig, and also
they grow much faster. When I use TG1 or JM101 I can pick colonies in
the morning and they are grown for minipreps by lunch. If I used JM109
or DH5a it takes much longer and I can't get the minipreps done,
digested, and the gel run in the same day like I can with faster
growing strains.

Michael Benedik
Department of Biochemical Sciences
University of Houston
benedik at uh.edu

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