" Septeaber 25, 1949.

Br. Samet J. Sjl,
Dept. BacterLology,
Washington Univcralty Medical Sctjool,
St. Louis 10, Kk.
Dear Aji:

Under soparate cover, I hav sent you F. coli Kel2, wild type, and #58,
& biotinloes mutant. Tho amtant was Lsolated by Dr. Tatum, who has deseribed
it briefly: PNAS 30: 404, 1944 ard IPC 169: 455, 1945.

Lr. He A. Lardy of cur biochemistry departnant hae had sono work done
on this mutant frou the polat of view of replacement of the biotin ~aqztrement,
and it alght ba be your advantage to coaminicates with hin 4f your interests
lie in this direction. |

#58 may be sufficiently unstable os to require som caution in its user
retsolate from nutrient agar, cr othor complete madius; use small inocula
and if posaibje, avoid prolonged incubatLonnperiods which select for biotin-

é

independent reversions.

Dr. Bernard Davie, in N.Y., probably has additional biotinleas mtantes of

- Be cold if #58 should be unsatisfactory.

With best regards,

Yours sincerely,

Joshua Lederberg
Assistant Profegsor of Genetics,