October 5, 1959
Dear Jacques,
I am now finally in my new lab at M.I.T. and almost ready to do experiments (after weeks of frantic waste of time).  During the summer I only managed to make some crosses, which indicate that the Pl dl element is transferred in a very funny way from Hfr to F- strains.  I have not yet enough data to interpret it.  At any rate, this permits us to construct mating products carrying Pl dl and I wish to study where this is located and how it interacts with the lac genes already present.  For this, I need a strain which is F- inducible and with a z- mutation as stable, say, as the one in 2.340.  In fact, strain 2.040 would be nice.  Even better, would be a strain lysogenic for lambda (or at least not lambda^r).
Also, I must ask you for another sample of 2.340.  In the moving and so on all our cultures of 2.340, by a series of coincidences, have been misplaced.  Can you send this also, very soon?
I hope in a week or so to start studying properly, in a less preliminary fashion, the initiation of enzyme production after infection with Pl dl.  I am aware that a number of problems that we discussed can now be tackled better with "sexduction", and most of these experiments are probably well advanced.  In fact, could you or Francois let me know the exact status of the F problem, beyond the note in the C.R.?  Still, I think we must clarify the Pl dl situation, which offers the possibility of studying the role of immunity in the function of the z+ gene in phage.
There is another point that I would like to know: maybe Francois could write me about it.  Is it possible to use an Hfr strain as an acceptor in mating, and if so, under what conditions and with which results?  I have seen no mention of it in the modern literature.  I would like to cross my Hfr lac deletion (Pl dl) in the other Hfr's lac- to construct a variety of strains carrying Pl dl. I suspect it won't work, however.
Do you have a copy of the Pajama paper?  It is not yet out and we really could use it.  Thank you very much and best regards,
Cordially,
S. E. Luria