@ovember 2, 1951.

Dr. Mortimer P. Starr,
Denartment of Bacteriology,
University of Ca.ifornia,
Davis, California.

Dear Mort:

We have recently completed "SRP" screening tests on the set of cultures
you had sent us a few months ago. I am fairly certain that I wrote to you
dn thanks and acknowledgment about the tine they were received, but can't
find the carbon, and am not sure just what J wrote.

From the labels, I gather that many of the cultures were appreciable resis-
tant to streptomycin. As my previous letter may have lamented, these are not
suitable for SRP testing. .

There were 38 cultures altogether of which a suitable test could be made.
None of these 38 appears to be fertile with our tester stock. Except for two
or three which fermehtdd cellabiose, or which appeared to be rather guazy,
they looked like typical &. coli.

This type of negative result is no less interesting than the finding of
interfertile strains in other collections. I am almost convinced that there
4s a real difference in this respect between 4solations of human origin, and
those of other sources. However, except as they generally conform to type coli,
the interfertile strains show no obvious distinctive cultural or serological
properties. This is ail the more reason for the further examination of type
and deviant forma from various sources. If you can give us any further assistance
in this respect, by way of further dsolates of (streptoayein-sensitive) coli,
X should be most grateful.

Would you give us instructions on the disposition of the cultures and glassware?
I will be glad to have the tubes Cleaned up and returned, although this will
take some time. On the other hand, most of the glants are still intact, ani
could be returned to you if you should heave recalled any further use for theg.

Yours sincerely,

Joshua Lederberg