MacConkeys instead of Xgal/IPTG

Greg Denomme denomme at FHS.CSU.MCMASTER.CA
Tue Aug 31 05:04:03 EST 1993

In a previous article, haviland at wrote:

>In a previous article, rrumpf at (Robert Rumpf) wrote:
>>I've heard that the alpha-complementation-based color selection using 
>>lacZ-phagemids, lacZ deletion host cells, and Xgal/IPTG plates can also
>>be done
>>using the same phagemids/host cells but plated onto MacConkey's agar.  Is
>>true, how is it done, and what's the mechanism for color selection?  I 
>>appreciate any help you can give...

>Hi Bob:  I'd strongly suggest that you look up
>Jennings and Beacham in Biotechniques vol 7:1082 (1989).
>Once our lab lacthed onto this method we rarely plate our ligations on 
>anything else unless dictated by a particular vector that doesn't have the  
>Betal-gal.  What is critical is that the bug of choice have the lac 
>deletion.  HB101's don't work, but Sure's, JM109, TOP10F' and others work 
>just fine.  At the time of plating you just put in 10 ul of 100mM ITPG and 
>voila!  You have red/white color selection.  One thing though, over time 
>your white (recombinant) colonies will turn a slight shade of pink making 
>colonly selection after about 24-48 hours very difficult.  So if you do 
>your ligations one day and will need to pick on another (for whatever 
>reason), then one must mark which ones to take or not to take.
>Hope this helps,
>+  David L. Haviland, Ph.D.	     Internet:"haviland at"   +
>+  Washington Univ. School of Med.   A.K.A : The Compiler                 +
>+  Dept. of Peds./Pulm. Box 8116     ICBM-Net : Just hit St. Louis        +
>+  400 S. Kingshighway               &-6  <- User is Brain Dead...        +
>+  St. Louis, MO  63110              FAX: 314-454-2476                    +
>+  (314) 454-6076                                                         +

Further to this discussion:

Pendola and Palis have reported that MacConkey-II lactose agar from Becton
Dickinson Microbiology Systems is able to distinguish recombinant plasmids
(Puc-9, pBluescript, pGEM-4) without the use of IPTG (Trends in Genetics,
Vol 9, pg 3, 1993).

Greg Denomme, PhD
denomme at

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