Slow growing XL1-blues

eric c. anderson anderson at
Fri Jul 29 10:49:24 EST 1994

In article <1994Jul27.213302.1 at>, fsajb3 at

> Anyone have experience with this problem?
> 	Our lab has been transforming XL1-blue chem comp cells (made competent
> in our lab using FSB protocol) with various pBSIIKS constructs. There has
> been no problem getting transformants, but the colonies grow extremely slow,
> and there is a really long delay before any blue color develops for blue/white
> selection. I checked to make sure we weren't overdosing the plates with
> ampicillin, everthing seemed normal. We are using bluo-gal and 100mM IPTG for
> color selection. Any information is greatly appreciated.

i've had the same problem, but was assured by others in the lab that it's
just a quality of the cells.  they always grow slowly.  i've encountered
similarly slow growing strains with invitrogen's INVaF' cells.  i also
think that color selection in general takes a bit longer than the actual
cell growth does.  i usally leave plates @ 37 degrees for 24-36 hrs, then
leave them at room temp for another 12-24.  the time at room temp slows
down cell growth but allows for pretty good color development.

you aren't doing anything's just the way they work.

as a marginally humorous aside, i just noticed that you're posting from
alaska.  i don't know what you consider room temp up there (maybe 5-10 C),
but down here in the heartland it's 24. :)

good luck,


eric c. anderson
anderson at
660 s. euclid box 8103
washington univ. school of medicine
dept of molecular biol. and pharmacology
st. loser, misery 63110

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