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Dear Luca:

Page proof has just come in for our paper in Genetics. As you ses, it
has now been advanced to 1952, vol. 37:720-730, and the proofs for the JGM
should be corrected accordingly. As only one of the two copies has had to
be returned, I can enclose the other. 200 reprints were ordered for you
and should be shipped directly to you. The issue is expected in about a
month.

There is very little additional bo report. Hfr recombination appears to
be about 100x as efficient under conditions of active growth as under any
other that we have tried so far. The existing data are not yet comparable
with the previous F+ x F- crosses; Nelson is working on this. It appears
likely that a similar requirement for growth conditions is needed in the
latter crosses, selecting for prototrophs. Nelson finds that when one does kinetic
experiments , mixing the washed parents and then plating at various times
that not only the background ("plate recombinants") but also the slope is
increased in unwashed, as compared to thoroughiy washed agar. The Likely
interpretation seems to me that mixed clumps are formed in the suspasaions,
and that growth conditions are subsequently heeded to allay the clumps to
go on to zygote formation. It is impossihle to prevent growth altogether,
owing to syntrophism. This may mean that the Maccacaro-—Booth phenomenon
is less trivial than appears at first sight: that is that residual growth
does more than increase the probability of interpenetration of microcolonies.

more about this, as it might be useful in the same connection.

With Salmonella, I have been looking into the genetiy mechanism of phase
variation. It looks very much as if alternative phases are both represented
in any one strain by factors at two loci, but that one or the other is some-
how inactivated. This inactivation is not only for its phenotypic expression,
but for its transmission by FA. I speak of inactivation, rather tha loss as
the cell "remembers" its original second phase when the first phase has been
substituted by transduction. As a by-product, many new Salmonella types and
some old ones have heen reconstituted. The story may bear some relationship
to heritable Rauefmodifications or somatic differentiation, but# there is no
indication that it has a cytoplasmic basis: i.e., the "inactivator" ig associ-
ated with the locus in transduction.

Thank you for the reprints of the x Scientia and W.H.O. papers. The latter
was admirable writing (and experiment). I have also seen the full chloromycetin
ms. (via Szybalski). Would the gradient plate technique not have been useful
in scoring progeny? The Pallanza report also arrived (but only a week ago,
having been long awaited). Would you like to give me explicit directions as to
its further circulation? We can copy the few pages we would like to have.

Barigozzi's formal invitation Just arrived-- again sans mention of financial
help. I shall reply as if I were attending (which may or may not be). Thank you
for any of your own efforts on my behalf.
Spicer is now busy working here for a few months on a WHO fellowship. We
are enjoying his visit very mich, as we did that of his predecessor (Bruce Stocker).
Like Stocker, 3mamsckx Spicer is working with me on Salmonella.. I realize that
your present improved position may make it less likely, but I hope that you will
not forget altogether if an appropriate occasion should arise to think about
enjoying our hosphtality yourself. Given enough time, I think we could make a
very substantial contribution to your living expenses [which wouldg unfortunately, J
depend on your securing a regular visa](perhaps $300-400 per month, which is not,
I realize, minificent-— but sti}, got uncomfortable even for a family). Please
regard this mammmuunieememomioh as a hopeful sufgestion tc create the meand
for a closer ccllaboratdon.

 

     
 

Are you acquahnted with Dianzini (Genova) and his transformation experiments?
They seem to be not so well controlled,as one would like, but may have some features
of interest. Unfortunately, Austrian (in a recent review Bact, Rev,) rather improperly
quoted a mild comment I had made in MGB which, I hope, has not been offensive.

While I remember, could I ask you the favor of furnighing addresses for
the following Italian scientists, as listéd. I have seen their papers usually as
titles or abstracts only and would like to enquire further:

Muremtsey, S.N. “Annali d'Igiene" 12:379-384 I problema della ibridizzazione
vegetativa in microbiologia. I have not seen the paper; journal not

available
Ziront (loc. cht. Bizzari) 10:277~284

Denes, G. G. Bati. ¢ Lum. 15:60-78 1935 Journal not available
Bizzari,M.Boll. Soc.Int. idier. Sez. Ital. 9:260-262 1937 JL. not available
Ciantini new develupments since 1944?
S A ae te m7 ‘gf
These maf all have to do with "paragglutination"——mI am collecting notes for
a comprehensive review I may sometime write. If you know of any other comprehensive
sumiaries of it during the past 15 years, I would be grateful to hear of it.

Sincerely,

Joshua Lederberg