April 3, 1953

Ref: MEDEC/ZIBP
Dr, L. 3. Baron
Dept. Bacterial Physiology
Immunology Division
AMS Graduate School
Washington 12, D.C.

Dear Ur. Baron:
Thank you for your note of March 27,

If you would iitke to whait here. could vou make it on and after May 19?
You are welcome to stay any reasonable length of time: Tesuspect that you
could learn all you needed in two or three days. If you were to stay any
donger period, [ woulda ask that it be not less than 10 weeks to enable the
compistion of any experiments started.

in the course of other work, we have included some experinents with
S. typhi strains. A mumber of antigenic substitutions, for the d:— H
complex.are recorded on the enclosure. Strain 6-901 4s, of course, readily
revertibie—~ in fact, 80 much sc that we have rather stayed away from it.
However, there is no doubt but that above and beyond its spontaneous rever~
tibliity, motility can be trandtiuced to 0-901 from any of a variety of
motile and non-mtile serotyres. Spicer has made some ineidental experiments
with Vi- S. typhi, but none explicitly designed to transduce the Vi factor.
I have my doubts that the mouse is the bast selective agent. but will detail
these with you during your visit. You will no doubt have studied Felix!
commentary on the history and behavior of the 901 strains (J. Hyg. 49:94-95),
which are very pertinent to such experiments. Our own experiments on the
transduction of various markers with the Vi~typing phages have bean incon-
clusive. The most clearcut results in tranaduction experiments kewéinue to
be those involving the phage "PLT22", originally extracted from a lysogenic
3. typhiouriun.

Please thank Mr. Abrams for sending me 5. napoli #187. I fear. however, that
this 1a the same atrain carried by Edwards under this number. Have any other
isolates of this serotype been preserved? My letter also asked about a set of
nonmotile Salmonellas deposited by Dr. Bruner during the War. Have any of these
been saved?

Yours sincerely,

Joshua Lederberg