AKAROA
ZOO

Department of Medical Genetics

June 3, 1957

Dr. Peter Mitchell
Biochemiatry Unit, Zoology Dept.
Weat Mains Road, Edinburgh 9, Scotland

Dear Peter:

I hope you can forgive me for the inordinate delay in replying to your letter
of April 8, especially when I had promised in advance to comply with it. I can
only pleadesome atypica} distractions from the work that had piled up, and in
connection with this new department.

I don't have the strains of the ML series, but I can give you the comparable
mutants of E. coli strain K-12, according to table 7 of the paper in the Dec. ‘56
Ann. Pasteur Inst. Accordingly, I am sending you the following:

Kel2 Wild type Lac’ & ML30 } Please keep in mind that both the permease
] and galactosidase of these strains, where
W-2241 sd-called cryptic Lac,” * ML3] present, are inducible.

W-2441 received from Monod as 1301-1 and purportedly ‘constitutive cryppic'
W~1317 Biddkdd Galactosidase-constitutive * ML-308

W327 Lac, Sua" = mltose-positive, glucose hegative (of Doudoroff, Has sid,
Putnam, Potter? and Lederberg, 1949, JBC 171:921.)

I've not had much more to say about these strains since 1951 (CSH Symp. 16 and
Genetics in the 20th Century. \+-1317 was selected by means of neolactose). I will
be interested to learn how far you concur with Monod's imputations.

You were most hospitable during our vieit to Edinburgh, and especially generous
in lending your shaver--which was one of the most comfortable I have ever used.

We have about 8 weeks now before leaving for Australia (for 3-4mos.) and I don't
expect we'll get any more done with protoplasts or I-forms, except to write up
what we have done so far. We have succeeded in isolating some genetically blocked
L~fhype mitants in BE. coli K-12; these have so far proved to be DAP-auxotrophs. I
should think you might be interested in these creatures: Elizabeth Work could furnish

you with Davis! strain, if you were ; this one is perhaps better worked over than
our new ones.

With best regardsg
Yours sincerely,

Joshua Lederberg
Professor of Medical Genetics