Dept. Genetics
University of Wisconsin
Madison 6, Wise

Communicable Disease Ctr.
Chamblee, Georgia.

Dear Dr. Groman:

Of course we have a community of interest on the induction of
toxicogenicity in C. diphtheriae!

when I first s8W the Freeman-Morse and Fra@bisher papers, I won-
dered #f transduction might be involved. It seemed to me not, if
phage could be passeé on a negative strain, and subsequently induce
toxe the same strain. Is thie true?

To put the sare question another way, does every culture that becomes
lysogenic also become tox? If there is a constant association between
tox. and lysogenicity, regardless of the immediate previous host of
the phage, it is not likely to be transduction imxprakiniz as seen in
Salmonella. In this system, the role of phage seems to be entirely
the carrying over of genetic factors from one host to another. If
the association is inseparable, the phage can, hardly be regarded age
a casual, passive carrier. In Salmoyella, eng phage particle
has a probability of only about 107% of transducing a particular trait.
Under special circumstances, a phage particle can discharge its
genetic passenger without itself initiating lysogenicity, but this is
exceptional.

Another system that seems to recuire lysogenization per se, and not
incidental transduction by the phage, is the determination of Vi types of S.
as studied by Anderson. Here too, most if not all cells infected with typhi
the appropriate phage are correspondingly altered in Vi-type.

The points of difference you mention are cntirely quantitative. If
your system is transductive, it might be much more efficient than Sal-
mohella. In addition, lysogenic Salmonella can be induced ¢by UV) or
aging)to release quite high titres of phage. The more @ritical experiment
is whether lysogenicity is by itself a sufficient, as well as necessary,
condition for tox. If not, it will have to be determined whether the
effixkciency of a given phage prep. depends on its previous history
in or on tox. wBe nontox. strains.

Please give Dr, Roman my best (if he's s$ill on campus).

Sincerely, —

Joshua Lederberg