UNIVERSITY OF ILLINOIS

DEPARTMENT OF BACTERIOLOGY

362 NOYES LABORATORY OF CHEMISTRY
URBANA

June 1, 1956

Dr. Joshua Lederberg
Bepartment of Genetics

The University of Wisconsin
Madison 6, Wisconsin

Dear Josh:

Under separate cover I am sending a copy of the
strain KM. We keep it on medium in which lactose is the
sole carbon source. This prevents it from reverting to a
lactose-nega tive, lysogyme-resistent strain, Essentially,
we employ McQuillen's medium. We make protoplasts in .5M
succinate, pH 7.7 with 200y lysozyme per ml. The experi-
ment you suggest, we are preparing to do in the near future,
The problem of getting suitably marked strains has slowed
us down in that direction. However, we have had plenty of
other things to keep us busy. I should like to hear some-
times how you make your coli protoplasts.

I conveyed your kind thanks to Lu and to Gunny
who both send their kind regards.

a

Sincerely yours,

SA

S. Spiegelman
Professor of Bacteriology

8S: 4jb