August 16, 1956

Dr. Louls Dienes

Department of Pathology
Massachusetts General Hospital
Boston 14, Mass.

Dear Dr. Dienes:

Among the enclosed reprints, I believe you may be specially interested
in the preprint on penicillin-induced protoplasts. It is of course obvious
that this finding is a direct extension of your own work, differing primarilg
in ite emphasis of quantitatige and enzymatic relations.

I have not, over tye last several years since my visit with you, lost
interest in L-forms, and this recent work has only renewed my active concern
over them. I have not, however, succeeded in preliminary attempts to secure
further outgrowth of protoplasts as such, i.e., they are fully viable, and
can increase tremendously in size, but have not been observed to divide
except as they revert to rods. A plausible view of large bodies on this
basis might be that they represent either mutants, or a penicillin-inhibited
physiological state, inwhich wall synthesis is largely, but not completely
inhibited, and our further effo-ts will be directed along this working
hypothesis.

My immediate aim would be to secure the outgrowth of protoplasts as
L-type growth in E. coli K-12, but to do this it seems important for me te
regain some familiarity with L-growth in more favomble material. I wish I
had been able to maintain the L-form of Proteus 52, which I took back from
your laboratory in November 1953, and which I did succeed in propagating
accordin: to your instructh&ons. I do have the lyophilized cultures of this
Proteus, however, and have begun to revive then,

As I recall both from my own experience, and your advice, the recently
prepared L-form from Proteus 52 has a marked tendency to revert in the ab-
sence of penicillin. It might save me a considerable amount of time for som
of these studies if I could also deal with the stabilized form, such as you
gave me a subculture of in 1953. Have you maintained this? Would it be
feasible to send it to me? (This is the one which was propagated by flotation
on the surface of broth; as I recall, however, it would also grow reasonably
well on nutrient~gelatin-agar (mothlity agar)).

You have also mentioned the propagation of Salmonella typhimurium L-forms
in thioglycollate brotg. This suggests the most pramising approach for my
own problem; do you have any cultures growing in thia medium now that you
could send me?
Finally, I have to admit that I have never studied sither S. moniliformis
or PPLO forms as muxk such. Could I impose upon you for cultures of these too.

This igs a large order. I am ssking you for
l. stabilized L forms from Proteus 52 (flotation form)
2. L-forms of S. typhimurium, growing in Brewer's medium
3. S. moniliformis (capable of transformation into L,)

4. Any "typical" PPLO.

I would not ask such un imposition if I did not already respect your
generosity, but for the same reason please to not go to any undue trouble
if you sre not mintaining these mterials at ready hand.

With best resards, C
f
a
Yours sincerely,
y
Joshua Lederberg
Professor of Genetigs