Antibiotics for M9 growth?

Michael L. Sullivan mlsulliv at
Thu Feb 17 16:19:31 EST 2005

I don't think these are going to be viable alternatives. I believe 
people like using carb in instances when the pH is expected to drop 
because it is more stable than amp at lower pH (also the reason it is 
used in plant tissue culture media, which is usually at an acidic pH).

As for adding amp daily, I don't think that will do much good on it's 
own, since beta-lactamase is secreted. My understanding is that it 
doesn't take very much beta-lactamase in the media to VERY rapidly 
inactivate added ampicillin.

What I know about this comes from Novagens manual on the pET system, 
where this sort of thing is often an issue.

I think the answer really is to go with another marker. In the end 
the small time investment now will probably be worth it.


>A coworker in my lab is planning to grow deuterated protein in E coli
>using minimal media.  The problem is that his plasmid carries Amp
>resistance, and the growth is projected to take about 2 weeks.  Since
>ampicillin isn't stable over such a long time, we have been trying to
>think of alternatives to recloning his gene into a KanR vector.  Two such
>suggestions are using carbenicillin instead of ampicillin, or refreshing
>the growth with ~100 ul of ampicillin every 24 hours.  Are either of
>these viable alternatives?

Please note new phone and fax numbers below

Michael L. Sullivan, Ph.D
Research Plant Molecular 
U.S. Dairy Forage Research Center
1925 Linden Drive West
Madison WI, 53706

(608) 890-0046 Phone
(608) 890-0076 Fax

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