September 25, 1951.

Dr. C. E. Clifton,
Department of Bacteriology,
Stanford University,
California,

Dear Dr. Clifton:

We are starting to do some serological work with the new interfertile
atrains of Escherichia coli described in the enclosed rephint. It would
be gratifying to be able to use strain K-12 in this work, considering
the backlog of information we have on this strain. Unfortunately, our
cultures are extremely rough, and have almost completely lost their
somatic antigen. I wondered whether you might not have a better culture,
or might perhaps know whether {t had been lyophilized in your laboratory
or elsewhere prior to 1944.

If you have any other E. coli strains that you think might be worth
while subjecting to a very simple test for croasability, I should be grate-
ful for the opportunity of testing then.

Sincerely yours,

Joshua Lederberg.