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UNIVERSITE DE GENEVE

INSTITUT DE PHYSIQUE Geneva, September 27., 1956

LABURATOIRE Db bivrdslgla

Professor J. Lederberg
Too Dept. of Genetics
ue University of Wisconsin

nn Madison 6

“tT Ce,
( mh Wisconsin USA

Dear Professor Lederberg,

Thank you very much for your letter. W. Arber, in
my department, is-indeed prepardng a thesis on defective lysogenic strains
and he now concentrates mainly on those obtained in transduction experiments.
His main results are the following ones:

1) There is segregation, as you described, into stable Gal”"immunes", but for
other strains also into Galt+Lp®, Gal~Lp‘.

2) All such heterogenotes studied (6) are induced to lysis by DV.

3) Active phage is never produced after UV-induction (e.a. lass than 1078)

4) All strains studied recombine after induction with superanfecting phage
(experiment made in using genetically marked W's).

5) Two types of such ‘inmmunes" are found; one of them multiplies the defective
X-DNA after UV, the other does not. (By experiments of the Jacob's type:

proportion of the recombinants in function of the time between induction and
superinfection).

6) The morphologies] study of the lysates of 4 strains in the electron microsco-
pe showed neither tails nor empty heads. (In the opposite of 6 other
“elassical" defective strains already studied, about which we will soon
send gou a M.S.)

7) In genetic phage-recombination experiments, the stable immune obtained
after segregation behaves exactly like the heterogenotic¢ "parent".

8) When induced heterogenotic Galt "immunes" are superanfected with active
genetically marked \, a part of the vrogeniture transduces Gal*. The pro-
portion of transducers is about equivalent to that of recombinants. The
Gal* obtained are mostly Gal*Lp™ and heterogenotic.

If I have weal understood your idea of a hehogenotic Lp’, I
think that these results do not fit. May be that your strains behave different-
ly from ours; in fact, we doy not use the same initial bacterial strains as
you.

I would be very glad to continue exchange of results and I hope
you do not mind us doing experiments in a similar direction.

I appreciated very much receiving your reprints. Having déne
research on figlobular forms of bacteria ourselves, we were very interested by
your M.S. on protoplasts. (We prefer to use "globular form" as long as the
deficiency of the membrane is not defined; we use "protoplast" for the Gram
positives when a defined substance is dissolved by the lysozym.) For the last
year, K.Gordon Lark (now at Microbiol. Dept., St Louis University, Medical
School, St-Louis 4) worked here on the mechanism of the induction off globular
forms by Penicillin. He used a strain of Aerogenes faecalis which had been
once isolated by RBonifas in my laboratary and which has the peculiar feature
of being able to multiply in its globular fZorm. We got globular forms also
with Kl2, but did not succeed in having it maltipliing in this form. For

the "faecalis", Lark found a specific growth factor in tryptone mediun;
without this factor (in synthetic medium) ordinary globular fomms are obtained
which do not grow but are viable.

Many interesting problems had been cdnsidered but not yet underta-
ken; infection and lysogenization of globular forms by phage DYX without
protein coat ; study of the eventually missing phage-receptors on the membra-
ne; possibility to transform glebular forms by DNA coming from genetically
different bacteria.... For the moment being, we do not work on these particu-
lar problems.

I will be very glad to hear from you again.

Very sincerely yours

oor

. . *
“ ap chet cet - CE v Coe LLLE ie ——
os a

Edouard Kellenberger
Dr @s se., Privat-Docent
Head of the Biophysics Laboratory