March 8, 7951

Dr. fe H. Ewing,

Enteric Bacteriology Laboratory,
Communicable Disease Center, Fell. Se,
Box 185, Chamblee, Georria.

Dear re Ewing:

Dre “dwarde mentioned that you had been preparing serfafor typing
0 antigens of E. coli, and that you might also be developing K and H
sera. I have lately been looking for new isolates of £. col4 which
show genetic recombination with the original K~12 strain of Tatum and
nyself. From about 350 Leolates from various sources, about o dozen
have bsen gleaned which probably recombine. 4e have been developing
naterials for eerological studies on these otraiite, and Dr. Kauffmann
has been kind enough to send representatives of the 25 mmbered 6
typea. However, our facilities for this kind of work are rather limited,
and we cannot hope to prepare all of the necessary sera reculred
for direct typing in the comprehensive scheme.

I an writing to ask whether you would be willing to type some of
the isolates which seem to be amenable to recombination analysis. “hie
information would be very helnoful in planning which ctratina would be
most worthwhile to emphasize for further lummogenetic work with our
facilities.

In hones of your favorable consideration of tuis request, i an
sending under senarate cover a grow of ten (or 30) c&ltures with
designating labels Y&-1, 7-2... -10 . All are of human (feces or urine)
origin, excent WG-2 which was isolated from chicken feces. I reslize
that some of these cultures may ba difficult to type owing to apon-
taneous agglutinability, eapeclally after boiling, but hope this will
not be an insuperable difficulty. ¥G-1, which exhLbite this diffiealty,
is the original Ke-12. de have a fairly comprehensive picture of the
cultural and biochemical character of these atraina, and will be glad
to forvard thia if 1% would be of any ure to you.

if, for any reason, you cannot widertake this faver ot the present
time, nlezne feel free to diapose of the cultures, and I will await
your later word when i might send then again.

Yours sincerely,

ky
/ Soshua Lederberg,
Associate Professor of Genetics