NEW YORK UNIVERSITY-BELLEVUE MEDICAL CENTER

NEW YORK UNIVERSITY COLLEGE OF MEDICINE

550 FIRST AVENUE, NEW YORK 16, N. Y.

DEPARTMENT OF PHARMACOLOGY October 1, 1956 OREGON 9-3200

Dr. Joshua Lederberg
University of Wisconsin
College of Agriculture
Madison 6, Wisc.

Dear Joshua:

Sorry to hear that you lost 173-25. If you were a graduate student I would
ecritigize you for not realizing that penassay brcth probably does not )
contain DAP! Anyhow, we make this mistake every once in a while too since its
hard to realize that these soups bacteriologists have cooked up don't contain
everything good in life. ,

We've had no trouble with reversions from this culture, and find it
satisfactory, for ordinary purposes, to keep the strain going and to experiment
with it using a DAP-containing filtrate as a source of DAP. This permits us to
save our limited supplies of the pure compound, which is not commercially
available. I'm sending you not only a fresh certified slant of 173-25, but
a slant of lysine auxotroph 26-26, which accumulares DAP. If you grow this bug
with vigorous shaking in minimal medium containing a limiting amount of lysine,
such as 10 4/ml., you should accumulate after two or three days between 100 and
200 /l. of DAP. You can easily make a rough assay of your DAP accumulation
by using 173-25 in the presence of lysine, on either soled or liquid mediun.

I think the enclosed note on penicillin is fine, and I've taken the liberty
of pencilling in a few minor suggestions. I'm not sure that Science wouldn't
be a better place for it than J. Bact.

Here's the geneology of our lac. strain that interests you. We once
isolated an unstabl® lac” which we numbered J1-O, and which was lost. As
I mentioned before, this mutant seemed interesting because its rate of
reversion of the lac. character was not accelerated by UV. From wt we
derived J@-1, which required histadine, J2«10, which required pantothenate,
and J@-6, which required tryptophan. J2-6 begat J4-5, and -13, with respective
requirements for hist&édine and (serine or glycine) Finally, J4-5 begat
J6-2 and J6-6, with additional requirements for proline and for (isoleucine
plus valine], respectively. I'm trying to resuscitate these old ‘stocks, which
we have not used for years and may not have kept very will. Whatever is viable
will be sent to you within a few days.

Many thanks for your congratulations. Everything is going fine, though
we are by now running into the traditional difficulty with managing to get
enough sleep. Since he isn't yet a very good verbalist, I've not been able
to find any rhetorieal deviges that will get him to mend his ways. But he is
very cute. Best regards to Esther.

Sincerely,
Peveg
Bernard D. Davis

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