May 23, 1952

Dr. H. P, Treffers

Department of iicrobiclagy
Yale University Medical School
New Haven, Connecticut

Dear Pote:

I have a report that someone in your laboratcry haa been able to con-
firm Hayes’ experiment on the fertility of straptomycin—inactivated 58-161.
Elise Cahn has been trying to do the same fcr some tine, with almost com
pletely negative reaulis. cuspesaiong treated to the point of essentially
complete inactivation (10“ or lesa survivors per 167) have been completely
infertile, although there was some productivity of less drastically treated
ceils. I was surprised at this, because for a long time I nad dine S* x s®
crosses on sm~mininal agar, with fairly good ylelds in certain combinations.
On the other hand, there was probably little prompt bactericide. I haven't
done the inactivation aqerioents ayself, as yet, and so won't take responsi-
biiity for them, but they look to have been well designed. Perhaps we are
missing some polnt of technique. Tf so, 1t would be a great help to us if
we could heve the details of your confirmation. I have been in close touch
with Hayes, but this hasn't helped to clear up the possible discrepancy.

Do you think that under the right conditions, cells might be stopped from
further growth by the persistence of streptomycin, without any fundamentally
irreversible change? 1 suppose there's no way to answer this witncut a reagent
comparable to BAL for wetelepciscning. I don't sea the necessdipyfor any

rastic relnterpretaticn of genstic recombination, whatever the outcome of
the experiment.

We haven't cone anything at all with the atreptokyecin-resistance-mtation
regulator since our previous correspondence. To some extent, we'v3 been waiting
to hear from you. Have you had occasion to prepare the revcrt that you mentioned
in your last letter?

Have you evar looked lato straptothricic resistance? I criginally thought
it was always associated with streptomycin resistance, but in K-12 this is true
only at lower concantrations. Por higher levels of resistance, I suapect a
multi-step situation, indecendent of S™. But we're not deeply interested in
this, and I am only concerned with Sinding another selective agent 13 easy
to manage as streptomycin.

Sinceraly,

4/23 / 52 Joshua Lederberg