May 21, 1954
Dear Seymour:
As you probably know from having talked to Ruth Ben-Ishai, we have been quite actively concerned with nucleic acid metabolism, in so far as induced enzyme synthesis is concerned.  You can imagine that I read, with great interest, your recent note from the Federation Proceedings which you sent to me.
We have been studying a variety of purine and pyrimidine mutants with respect to the same characteristics.  You indicated to Ruth that you do not mind if we studied the thymineless of strain.  I would deeply appreciate it if you would send me a culture of this 15T- strain.  Luria had the strain, but apparently it has virtually completely reverted.
I hope I get the opportunity on my next trip East to see you.  We have some data which I think you will find of some interest.  With kindest personal regards.
Sincerely yours,
S. Spiegelman
Professor of Bacteriology