April 11, 1952

Dr. Jay Boyd Beat
Department of Physiology
University of Chicago
Chicago 37, Dlinois
Dear Dr. Best:

May I acknowledge your letter of the 8th concenning the Lac,” mutants
of Escherichia coli K~12.

Inasmuch as our studies on lactase adaptation in these mitants are
still in progress, and no definitive description of them has been published,
I would be reluctant to distribute them at the present time. I would not
say that E. coli was very favorable material for adaptive enzyme studies
(as compared, for example, with Pseudomonas fluorescens): it is quite
difficult to study the kinetics of adaptation in non-growing cultures.

It is only the groundwork of genetic analysis in this strain that would
justify its ude for these studies.

Please let me know if I may be of assistance in any other way.

Yours sincerely,

Joshua Lederberg
Associate Professor of Genetics