October 21, 1968

Dr. Joseph 0. Falkinham
Department of Molecular Biology
University of California
Berkeley, California 94720

Dear Dr. Falkinham:

We have a very substantial archives on E. coli strains, and if you are
interested in genealogical research I would urge you to come down here

for a couple of days and work your own way through these files. If you
have any specific questions I will be glad to answer them via this corres-
pondence.

—

I believe we have been rather fussy in our experimental papers in describing
the genealogy of our strains, and I am grateful that you are emphasizing the
importance of perpetuating such traditions.

WA

W1485 was isolated as a lambda-sensitive Fr mutant from E. coli K-12. It is
correctly characterized as Ft. This was, I have to add, not a character

known at the time of its isolation. Subsequently an F~ mutant, W2637, was
isolated from it by passage through motility agar (reference 67). I do not
know off-hand where to refer you to an explicit reference to this strain,

and just do not remember whether we have published much on it, or its deriv-
atives. W2637 was subsequently noticed to be a rather weak galactose fermenter,
but a "full gal+" colony was noticed on EMB galactose and was reselected for
further use as W3110. I trust you well appreciate it is very difficult to know
whether the weak or the strong fermenting quality represented the clone from
the immediate selection of the F- mutant labeled W2637.

WHH (VIA

W2915 has the history indicated on the accompanying diagram.

I enclose a number of sheets of rather ancient history whéch may interest you.
It has been about ten years since I have worked direct#y on E. coli genetics,
but I think we can resuscitate answers to any specific questions that you may
have and for which we had the information at the time.

I have made some other corrections to the best of my ability on a copy of
your pedigrees.

Sincerely yours,

Joshua Lederberg
Professor of Genetics