TS a

an

Yv Ca.Sl: E.
/CA.38: E.coli producing colicin E.

December 1, 1950.

Dr. Joshua LELEREERG

The University of Wisconsi Mes
College of Agriculture A ae A
MADISON 6. ,

Dear Dr.Lederberg,

\ . Y .
~~ 33) "3 2 Your letters dated Nov.2l1 and Nov.13 are here

and I thank you most expressly for your courtesy.
I am sencing the following strains:

wCA.T: (coli V of Gratia) E.coli producing colicin V.

A.18: E.coli producing colicin B.
-Ca.234 E.coli (IMVIC -+--) producing colicin D.
freundii producing colicin A.

 

“Ca.42: E.coli producing colicin F.
CA.46: E.coli producing colicin G.

-OA.53: E.coli producing colicin I.

YCA.57: paracoli (IMVIC ++-~) producing colicin C.

‘CaA.58: pigmentea E.coli producing colicin H.

VCA.62: paracoli (IMVIC ++--) producing colicin J ana I.

2K.235: lysogenic E.coli producing colicin K.

uP.7: Shealcalescens producing colicin Se.

"-P.9: Sh.sonnei producing colicin S3 + another one.
“pele: Sh.paradys. Boyd# D.1 producing colicin 651.

'P.14: Sh.dispar producing colicin 55.
/P.15: pigmented Sh.ogispar producing colicin S4.

VC.6: E.coli £ of GRATIA, sometimes designated Ca.@l, is the indi-

cator strain very susceptible to all these colicins except
colicin C (CA.57 has a slight activity against C.6 but is very
active against any strain of S.schottmuelleri).

If shali be glad to send some resistant mutants
but typing of the colicins is not as simple as you think, at least
not with every colicin. Resistance to colicines is very similar to
resistance to bacteriophages, cross-resistances are frequent, some
resistant mutant are very stable but dher are not and with some
colicins, like G or H,it wes never possible to get a true resistant
mutant. For example, cross-resistance is the rule towards colicins
E, F, J, S&, S3 and S5 (designated group E), the type-strains pro-
caucing these colicins loose all or part of their activity against
& mutant selected by any one of them but they ciftfer by other cha-
ructers such as range of activity against other strains, morphology

of the inhibition zone, susceptibility to proteolytic enzymes and
so’ on.

I have already mace some experiments with strains
K.1le - W.1364 and W.1116. K.1z2 is no colicin proaucer but hes 4 sus-
ceptibility quite comparable to that of my indicator strain C.6 ana
iaentical to that of its mutant W.1364. Susceptibility to different
phages of K.12 and W.1364 was also tested; they airffer only by the
resistance of W.1564 to phages T.1, T.5 and 1.7. I have already de-
rived from K.12 4 types of mutants resistant to different colicins

 

 
 

that I shall send you: WR.1 is resistant to colicins V ene, WR.< to
colicin a, WR.& is completely or partially resistant to all colicins
of group E and to colicine A, and WR.4 is partially resistant to coli-
cin K.

W.1113 which you refered to as causing direct an-
tagfonism was shown by my technique to produce « colicin active against
C6 ‘as well as K.12, may be colicin S.4.

I appreciete very much your offer of sending me
Suitable intercrossable cuitures of E.coli K.12 and shall be glad to
receive them as well as some directives for their proper uSe.

I am very sincerely yours.
Ks eh / cole.

Dr.P.Fredericq, Agrege.