UNIVERSITY of WASHINGTON
SCHOOL OF MEDICINE
DEPARTMENT OF MICROBIOLOGY
SEATTLE 5

February 2, 1953

Dr. Joshua Lederberg
Department of Genetics
University of Wisconsin
Madison, Wisconsin

Dear Doctor Lederberg:

During the past year I have been engaged in studying the phenomenon
described by Dr. V. J. Freeman concerning the isolation of toxigenic
C. diphtheriae from the phage-resistant growth of a non-toxigenic strain.
Sufficient quantitative data has been collected to make a theory of in-
duced change the only convincing hypothesis and consequently to rule out
the possibility of mutant selection by phage. As Freeman reported the
isolated toxigenic strains are always newly lysogenic, a fact which was
immediately suggestive of a possible role for phage if the change were
indeed induced. Other evidence which we have collected while not un-
equivocal is also suggestive of a role for phage.

Since it appears that the phenomenon is conceivably related to
transduction and possibly identical in its basic nature, I am taking
the liberty of writing to you. I have read the work which you and Dr.
Zinder recently published with great interest and from the data gathered
to date in my laboratory see two major points of difference in the
C. diphtheriae and Salmonella systems. First, toxigenicity is induced
in a relatively high percentage of the non-toxigenic population, some
Q.1%-7.7% having been converted to toxigenicity after a 20-30 minute
exposure to cell free filtrates containing phage. Second, on the
basis of some current work it appears that the agent inducing toxin
production is produced spontaneously by the converted toxigenic-lyso-
genic strain. Both of these differences could of course be quanti-
tative rather than qualitative in nature and the work currently under-
way is designed to establish the similarity or dissimilarity of the
two systems.

Rather than proceed with a more detailed account of the work at
this time it seems best to inquire first whether you are interested
in an exchange of information on this subject. Both Dr. Roman and
Dr. Delbruck have suggested a possible community of interest, and I
Shall be happy to do what I can to foster it.

Sincerely yours,

Dhol BChamon

“Neal B. Groman

Instructor
NBG:dic