September 15, 1949.

Dr. Bernard b. Davis,
The. Research Laboratory,
All E. 69 Street,

New York 21, N.Y.

Dear Bernie:

To date, I hadn't heard anything from Beadle concerning the proposed
course. I haven't given it any thoaight, and will have to wait until I have
had time to think about it, and have heard from Beadle before I can give
you any considered reactions. Offhand, I would think that Corona Del Mar
would be mch the better bet, in Auguas.

As I thought had been implied, the table of suggested concentrations is
almost, completely hypothetical, calculated mostly from the requiremsnts
of other organisms, with a large saféey margin included. You may be able
to revise some of the items on a more empirical basia if you have studied
the quantitative requirenents of the vitamin mtantsa, and would appreciate
your comneiis. fe have not locked for or obtained any B-l2 mutants.

We wili send you a couple of our prolineless mutants which were refractory
to penicillin.,very shortly. The observations were rather casual, but were
repeated on 5 different strains, so there might be something in it. You will
remember that our techniges differea little, mostly in respect to the length
of the penicillin treatment. 24 hours is too long for most of the bugs we
have used, but the Waksman coli strain would appear to be somewhat more resis—
tant than most. All of this might have a bearing on possible discrepancies
in our results.

With best regardsp
Sincerely,

Joshua Lederberg