AMERICAN CYANAMID COMPANY
1937 WEST MAIN STREET

STAMFORD, CONN.

TELEPHONE
STAMFORD 4-614]

 

December 10, 1946

Mr. Joshua Lederberg
Osborn Botanical Laboratory
Yale University

New Haven, Connecticut

Dear Jogh:

In answer to your letter of December 8, the mutant
strain of E. coli B which requires tryptophane and is resistant to
& (T1) virus is extremely stable. Wo reverted colonies, with
respect to the tryptophane requirement were obtained from about
1.5 x 10+ celts of this strain plated in tryptophane-free media,
although one out of about 8 x 10% cells are able to grow ata
somewhat subnormal rate with indole. I believe we gave Tatum a
culture of this strain (#1-415B) as well as of the parent strain,
E. coli B.

As to the other mtant strains, about all I could do
would be to list those which are relatively stable since we have
not compared the rate of reversion of the various strains, Among
the relatively stable strains might be listed the methionine, sulfide,
nicotinamide, arginine (series), indole, glutamine, uracil ani
thymine strains.

Sincerely,

AMERICAN CYANAMID CO.

Otay.

RRR: agm R. R. Roepke