Liege, way 24th, 1951.

Dr J.LEDERBERG

Dept. of Genetics
University of Wisconsin
MADISON 6 (Wis.)
U.S.A.

Dear Loctor Lederberg,

Thank you very muca ror your letter dated
May 10.1951. There are certainly very intimate relation-
Ships between phages and colicins, Lut I do not toink, at
least at the present time,that coiicins are incomplete or
Eragmented phages. Further work on the production of colicin
id by mutants of E.coli V resistant to phage T.1 incicutes
that this is a spontaneous mutation and that tne mutant pro-
ducing colicin mw is merely selected by T.1. Such awutants ure
also selected when colicin C is acting on E.coli V because
there is 4 cross-resistance to colicin C and phage T.1 as
well as te colicin M. For example your straimW1177 which
is resistant to T.1l is also resistant to colicin C whereas
the mother strain K 12 is susceptible. Non colicin-proau-
cing mutantj of V are not known so that it is impossible to

Getermine if the prior presence of V colicin is required
for M. colicin formation with 7.1.

AS you pointeu out resistance to T.1l and 1.7
is usually inuependant, at least when tested with E.coli B.
But with other susceptible strains, -aa mnong them E.coli V,
resistant mutants selected by any one of these phages are
also resistant to the & others. There is no cirference in
the activities of V/1 and V/7 on B/1,5 and B/? because they
act only through tnueir colicin V as B as well as B/1,5 ana
B/? are not Susceptible to colicin M.

AS regard tne transiation of "un mutant V/5
lysogene" you ure correct in thinking thet tuis is notttrue
lysogenic strain but a culture carrying resivual 7.5.

I just began some work on recoubinetion in
H.coli K 1g. Your 2 mutants 58.161 and W.1177 are most con-
venient to hanale. a iutant resistant to the 8 colicins Vy
B, D, E, G, I, K and S.1 was uerived in several steps trom
58.161 ana crossed over with W.1177. A wide variety of re-
combinants were obtained differing both in their resistance
to the different colicins as well es in their biochemical
eeeee properties. Ii you have any aiificulty in Obteining mutants

resistant to the colicins I snail be glaa to send you some.
AS you Kindly permittea further uistribution,strains

K.elé, 55.161 ana W.1177 were sent to Prot. WINKLER of Utrecht (

Netherland) at his request.

/
Iam very sincerely yours,
of f
A re

.
woe

ir. P.FRELERICG