October 31, 1952

Dear Dr. Rountree:

Thank you for your letter of September 2. I will try to answer
the questions you raised concerning the ms. on lysogenicity [which
is to appear in the January 1953 issue of GENETICS].

Your first point had to do with the transfer of prophage to
a "sehsitive" ceil. Let us condider the segregation from hetero-
zygous diploid cells.(ms. p. 9 and table 3). If a seprate nuclear
factor is involved, as you suggest, and if the diploid parent cells
are infected with mature or potentially mature phage, then the Lp’ (Gal-)
segregants should be uniformly infected with a iathak virus lethal
for that genotype, and should not be recovered. A certain fraction
would tecome lysogenic again. In fact, viable Gul- Lp are recfoverad
without @ifficulty, and very few Gal- are Lp* are lysogenic. We con-
clude, therefore, that "potentially mature phage" is not transmitted
to these segregants. We argue further that either 1) the prdéphage is
not transmitted to these segregants at all, i.e. that it is chromosome-
bound, or 2) that prophage, as it exists in Lp is unable to propagate
in lp , i.e. thatbit is distinct from the laabda of the lytic cycle
(not necessarily genetically; perhaps developmentally). In either case,
there is evidence for prophage as distinct from mature, albeit intracellular
phage. This weak conclusion is staeed on p. 17, and I do not think we
are in disagreement at all.

To come to your second question, experiments with lambda are complicated
by reversible adsorption. As far as our studies go, however, they point
to immine-1 (Lp,") as capable of adsorbing lambda, while immune-2 (Lp,*)

is not. The possibility that Lp? may represent some sort of bound lambda
was stated of p. 19-- it is still open. More recently, we have found

that Lp; can, very rarety, be made lysogenic. The behavicr of closely
linked markers suggests that this occurs when there is a transduction
of the Lp. locus (bogether with Gal”), so that the situation is very

complicated. Recently, this transduction of Gal,” has been found to

take place, in a way comparable to the transduction of a variety of traits
in Salmonella. But Gal, kx (perhaps also Lp) is the only locus for which

this experiment works in E. coli. All of this seems again to point to a
very intimate relationship of lambda with the bacterial chromesome.

Yours sincerely,

Joshua Lederberg