Thanks for your word on the lysogenicity of E. coli B. I shall be interested and amused to hear how this turns out.
We don't pick up very many purineless mutants, and most of our recent mutant hunts have been in Salmonella which I suppose
you will not care too much for. I am sure that you can get W-1926 (the diaminopurine-responding strain) from Guthrie: I don't
happen to have it in open stock, and would prefer to conserve the lyophil tubes for the present, if this is not inconvenient
for you. W-1926 is from a different line of E. coli than K-12.
I am trying to round up a few mutants we do have in K-12 to send to Seymour Cohen in a couple of weeks. It would be a convenience
to me if you could pick up copies of them directly from him.
P.S. Dave Bonner may have some other purineless in K-12.