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Ministére de |'Instruction. publique

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UNIVERSITE DE LIEGE

Microbiologie et-Hygione: “4

 

Prof. P. Fredericq

 

 

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Liege, le January 16, 1958.

1, rue des Bonnes-Villes

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Bo

Prof.J. Lederberg
Dept.of Geneties
University of Wisconsin
MADISON 6 (Wisconsin)

Dear Dr.Lederberg,

Thank you very much for your letter dated Decem=
ber 15, which arrived when I was away. I shall answer your different
questions in order:

1.- I have no reprints from the Ciba Symposium but I am sending by

' ordinary mail some other reprints.

2e- I am sending by air-mail some K.12 made colicinogenic for diffe~
rent colicins (all are derived from Wollman strain 112-12 which is
cystin-histidine deficient, gal.4—, T.ir, S.r, and non lysogenic;
any non colicinogenic K,12 may be used as indicator).

142-12/601. oy CA.18 and producing colicin B

TR.24 =

TR.25 = 112-12, "  " K,235 " " K

TR.27 = 112-12, " " TRL10 =" " " I + E(2)
TR.28 = 112-12. " "K.30 " " " E(1)
12-9 = 112-12," " Kg " n " I

12-94 = 112-12," "K.94 " " " Vv

Sem Te problem has not been studied any further. When both strains
are F- there is no transfer of colicinogenicity but if the colicino-
genic strain is made F+ then the transfer occurs. If the colicinoge-
nie strain is F- and the other Fy there is a transfer but it is as
yet not decided if it is a transfer from F- to Fy or if there is
first a transfer of F to the colicinogenic strain and then transfer
of colicinogenicity from F+ to Fy.

4.- Your suzgestion of using the symbol of plasmids for the colicino-
genic factors is quite valuable. I found it perhaps a little prema-
ture for 2 reasonss

a) I think that colicinogenic factors are more virus-like than
plasmid-like.

b) It would be quite coherent for the colicinogenic factor go-
,verning production of colicin E (1) but other results are obtained
ef other colicins that I am now studying. Particularly in the case
of colicin I there are some lethal effects which seem to be linked
to the selected markers used ,and to interfere with the trabfer of
colicinogenicity or immunity to it.

o.~7 I have-no indication of such a phenomenon because it is diffi-
cult (though possible) to disjtinguish immune cells from cells
which have lost the receptor,

6.- Thank you very much for your proposal to come as an honored guest
of your laboratory. In fact I am coming to the States next March to
stay 3 months at Cold Spring Harbor, I shall travel during June and
hope to be able to visit you on my way. I shall write to you about
it. As regard my coming to your laboratory, it is very appealing to
me and I shall be glad to discuss it with you. However I do not think
that I could come before 1960 or 1961 and in any case it would be
difficult for me-to be absent more than 3 or 4 months.

7.- I am sending strain CA.46 with the other strains.

bot (ol

prof.P.Fredericq.

Yours sincerely,