April 12, 1949.

Dr. R. Latarjet,
L'Inatitut du Radiuna,
2, rue d'Ula,

Paris 5, France.

Dear Latarjet,

I was very pleased to hear from you. I can spare another copy of
my article Heredity, and am sending it along, together qith some
repbints for the henefit of Dr. Fidas.

Lately, our work has taken three directions. I have been muddling
through the problem of gene-~ensyme relationships, parallel to what Monod
is doing, and he knows a]1 about this. Then, lately, we have found
peculiar mitant stocks of EF. coli K~12, from which heterozygous diploid
progeny can be isolated from crosses (rather than the immediate segregation
usually noted). These heterozygotes undergo segregation occasionally
(about once in every ten fissions) and we have been studying the genetics
of an aberration that may be associated with the persistence of the diplo-
phase. Finally, it turns out that K-12 is lysogenic, carrying a phage that
I have so far been able to detect only on a sensitive, non-infected
mutant from K-12. The sensitives can be reinfected, and become lysogenic
( about a quarter of the cells survivéng exposure to the phage). I have
been able to find a phage in sewage which is interfered with by the lysogenic
phage. Thus resistance to the sewage phage can be conditioned either by
gene mitations (V,", as it turns out) or by the acquisition of the cyto-
plasmic "character", the lysogenic phage. Aside from this, the lysogenicity
has no bearing on recombination. One of my students has been working to
look for recombination in Salmonella, but although the results are very
encouragine, lysogenicity 1s so common as to interfere very markedly in
the experiments. I have been trying to disinfectmlysogenic bacteria with
radiation (see p. 155 in my review article), but so far with only sporadic
success.

I wonder. if you can suggest where the famous lysogenic coli of Lisbonne

& Carriére might be obtained. Monod did not have it. If you could locate
this strain, and a suitable susceptible indicator, ¥ would be very grateful.
Meanwhile, I wonder whether you might not have considered that mutations

in the phage carried by lysogenic bacteria would not be especially pertinent
to cancer? (Viz. Burnet & Lush). Potter, et. al,, here seem to think they
have some fairly good evidence that the exhaustion of some cytoplasmic par-
ticle underlies the induction of liver cancer with azo dyes. My own feeling
is that cancer is some sort of genetic change, but that the question is still
open whether it is nuclear or not. Let us hear from you again,

Sincerely,