E.coli strain

[Chris Boyd]

davesmith at bioch.tamu.edu wrote:
: benedik at uh.edu (Michael Benedik) wrote:

: <<snip>>

: >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


: Thanks Mike! 
: You beat me to the reply.  Well said.   Thanks.

: I'd like to add that transformation efficiencies are no longer a real
: consideration due to the success of the Inoue competent cell protocol.
: Thanks to all who have participated in the discussion here in the
: newsgroup.

No I wasn't mixing up JM101 with JM103. JM103 was MEANT to be rk-mk+, but
as I understand it, those cultivars that are lysogenic for P1 have lost
the hsdR4 mutation and are thus rk+mk+ as stated.  (See Felton, J (1983),
Biotechniques 1:42.)  See also footnote a to Table 4.1 (page 4.15) of
Sambrook et al.  I'm not sure whether KK2186 is rk- or rk+, you'd have to
check with the original reference.

As for recA+ hosts growing faster, well this is just great: you can get
your minipreps done hours faster. Personally, I'd prefer to wait, using
a recA- host, and ensure that the inserts are more stable. If I want a
same day result, I use colony PCR.  But if you want to live fast and
dangerous, that's up to you.

If you think transformation efficiencies are no longer an issue, try
cloning a 5 kb insert into a 40 kb plasmid in JM103...

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