March 19, 1951.

Mies Isabelle Havens,
Department of Medicine,
University of Chisago,
Chicago 37, DLlinois.

Dear Mies Havens:

Thank you for continuing to forward the cultures of E. coli, etc.,
which are proving to be extremly useful in my investigation.

Until the last batch, none of the cultures had given a strikingly
positive result in my tests for recombination with F. coli strain K-12,
although a few interesting curiosities turned up~ 0.g., "Kurakowa—throat",
in your firet group was an unusual pigmented coliforg.

However, two cultures just received: 521245-sputum, and P526709-feces,
gave a clearly positive test. Can you give m= any further information on
the cultures or their source which might be of bacteriological interest?
It would also be pertinent to werify that they came from different indi-
viduels, although the cultures themselves are sufficiently distinct to
make it whikely that they are duplicate isolations.

A batch of gaterial received here on 3/12/51 was rather puzzling. The
tubes contained a fluid which may have been spinal fluid or serum judging
from thelr cegzulation after sterilising. Most of them were sterile on
transfer to EMB. I suspect now the possibility tmt there may have been
a slip somewhere,and I hope that my having disposedmof the material did
no harm. The tubes bore numbers like 5711, 5708, 6557, 4982, ete.

The used culture tubes ani mailing cartons will be returned shortly.
Most of the slants are coming through satisfactorily, with an cecasional
breakage which is probably harmless.

Youra sincerelg,
Joshua Lederberg,

Associate Professor of
Genetica.