Ref. 5076-LOE5C

September 15, 1952

Dr. Charlotte Colwell
Veterans Adminda&tration Hospital
Hines, Illinois

Dear Dr. Colwell:

Your letter and culturas were on my desk when I returned from
my vacation Saturday.

Thank you very much for taking the trouble to go over your ex-
periment again. I have streaked out the slants on nutrient agar and,
of course, promtly eaw the SCV for myself. fie will go ahead now to
try to repeat yout techhdque for making them. Might I ask for precise
directions on making up the synthetic medium? This seems to be the only
Way we could be going wrong. we have baen using MNQ us furnished by
General Blochemiculs.

We have picked up one lead that may be promising for other pur~
peess: UNY, cud probably benzoquinune alsu, have a selective effect
favoring auxotrophic mitante very sfallar to that show by penicillin.
It is not iupossible that this is the underlying mechanisa for the
production of the SCV. de’

Yours sincerely,

Joshua Lederberg