VETERANS ADMINISTRATION

HOSPITAL
HINES, ILLINOIS

 

September 3, 1952

YOUR FILE REFERENCE:

IN REPLY REFER TO: 5076=1OR5C

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

Dear Dr. Lederberg:

Under separate cover, I am mailing you 4-agar slants of
cultures of Escherichia coli II. One is the seventh picked colony
from the stock oulture, a suboulture of which (in synthetic medium)
was put into synthetic medium containing various concentrations of
2-methyl 1,4=naphthoquinone; that is, it is the parent culture of
the small colony variants. The other three are oultures of small
colony variants (S.C.V.) obtained by streaking after 48 hours' incuba-
tion in 0.00125% quinone. They differ from those described in my
paper in that they were obtained by repeated picking of S.C.V. As
I have told you, I was not successful this time in recovering S.C.V.
in pure culture on direct streaking of any concentration of the quin-
one, which I lay to the impurity of the quinone. They did appear in
comparatively large numbers in 0.00125% quinone, however, and by
repeated picking, I obtained these strains which appear to be stable,
although they increase somewhat in size on prolonged incubation.

If the S.C.V. are subcultured in Difco nutrient broth, and
the broth after 24 hours' incubation is streaked in agar, the typical
haze of tiny colonies in pure culture results, which I had previ-
ously noted with direct streakings of synthetic medium containing
certain concentrations of quinone.

We happen to have no use at present for differential media
for the gram negative group so we have nothing on which to test bio=
chemical reactions. We have been extremely busy and have not been
able to prepare it.

I trust that these cultures will serve your purpose. I shall
be interested to hear.

Very truly yours,
CL ter, A. Gtvece

CHARLOTTE A. COLWELL, Ph. D.

An inguiry by or concerning an ex-service man or woman should, if possible, give veteran's name and file number, whether
C, XC, K, N, V, or H. If such file number is unknown, service or serial number should be given.