February 18, 1958

Dr. P. Fredericq
Institut de Hacteriologie
Universite de Liege

1, Rue de Bonnes Villas tp
Liege, Belgium wer
Dear Profesaor Fredericq: jf |

Thank you very auch for the phage kins » which has met our
expectations ag a useful tool. Our work is going very smoothly
now, and I have succeeded in transfering colicin E to a number
of other stocks for the main experiments to be done soon. My
dmapression is that the colicin is transferred somewhat less readily,
in quantity concerned, than is the 3 factor. A closer examination
is needed,

I feel that i should tell you that the culture TR-27 is nixed.
It contains both a Gal* 3° and a dal” 3% comppnent. I think the
sam accounts for my previous report on it, in which there were more
ef the S® cells. May I burden you with onze more request? I have
already looked at a few Seluonellu strains w find one which nould
produce a solicin active against E. coli. So far this search has
failed, I am agticipating some future experiments where I may be
interested to st@dy the transfer of colicin between Salmonella ant
E. coli, Since you will be out of your laboratory later this year,
could I ask you for such a culture now?

+

I am looking forward to seeing you later this spring.
Yours sipcere}y ’
Joshua Lederberg
Professor of Medical Genetics

JL/ew

P,.S, I have meent to ask you one other question for some wots,

In several papers you mention your technique of testing for colicin
production by (1) seeding = plate with a colicin-producer (2) sterilizing
this after growth by chlroform vaper and (3) adding «© uniform lawn of
colicin sensitive bacteria. Oan you tell me in more detail just how you

accomplish steps 2 and 3, especially f§ step 27 Is it in a vacuum deat-—
cator or other chamber? How efficient is 1t7