May 2, 1952

Dr. Charlotte A. Colwell
Research Bacteriology

Bldg. 54 Room 16

Veterans Admindstration Hospital
Hines, Illinois

Dear Dr. Colwell:

Thank you very much for your courtesy in sending me your "©, coli II",
I have again repeated, several times, treatments with 2-methyl 1,4 naphtho-
quinone on a single col6ny isolate passed through several transfers in syn-
thetic medium.

I regret to report that I have still been unable to detect any small
colony variants as described in your 1946 paper.

Incidentally, this strain did turn out to be crossable, by the criteria
of the enclosed reprint. This will be very advantageous for any further
genetic analysis.

Z can well understand that you may be preoccupied with other problems
at the present time. If,however, you could find occasion to repeat this
experiment ypurself, I should be most grateful to hear the result. It is
not unlikely ‘that some subtle variation in method or materfal is responsible
for the discrepancy. I should not wish to undertake a complete rectifica-
tion without the assurance that the expsriment is roproddcible with cur~
rently available cultures and reagents. It would also be helpful to have
a culture of the dwarf colony form, so as to be certain that it would be
recognized.

Yours sincerely,

Joshua Lederberg
Associate Professor of Genetics