March 10, 1952

Drs. Bernard D. Davis and Werner Maas
411 East 69 Street
New York 21, N.Y.

Dear Werner and Bernie:

We spent all last week in Cincinnati. When I got back, I found your
shipment of Kit and K-12\NY]. I also found a lyophil tube of the Wakeman
atrain that I had forgotten about. Last night I tested them.

Your K-12 qnd mine agree. However, the Kit strain, the Waksman strain,
and ali of the pantothenicless cultures we received last summer are alike
in carrying a weak lysogenic phage active on W-1177 or K-12. The best
way to show the phage 1s to streak the presumptive carrier against W-1177
on ENB sm agar.

It seems most reasonable to conclude that the pantothenate mutants in the
Kl and KIT series are derived from =. coli aksman rather than K-12. I will
do some more tests to rule out the second possibility that your K1T somehow
became contaminated with the phage, but not the cells,from Waksman.

This substitution may have been extraordinarily fortunate, because the
‘question is now again open as to the crossability of Waks. As I recall, you
did a few experimants on this a long time ago with negative results. Judging
from the Kl- results, however, Wakes. may be interfertile with some of our
new golis. Also,aks not KIT as well as pnt+ reversion of Kl-, both fertile
with K-12 stocks? The whole story should be gone over again now, and I
hope you will let me join with you in it. Kl~ seems to be F+; 1 am rechecking
this with the Waks. itself.

Meanwhile, would peuyba willing and able to provide me with some suitable
auxotrophs (for crossing) from Waks., of independent d-rivation from the Kl line,
so that we can more easily tes}-cross Waks. against our other colis. If you
happen to have a diauxotroph S’ ready-made, this would help especially for
SRP tests aZadnst other colis in which we have not yet made suitable auxotroph
testers.

Have you summarized the cultural peculdarities of “aks? I have in mind
sugar fermentations, phage reactions, eté.

Sincerely,

Joshua Lederberg