July 3, 1952

Dr. Werner Braun

Mi Division Biclogiesl Labs,
Chemical Corps, Camp Detrick,
Frederick , Maryland

Dear Werner:

Your account of E. coli recombination reads very well, and there is
nothing in it that needs correction. The 1951 CSH symposium is now out,
and you may find our paver in 1% a useful recpitakation, in considerable
detail, of tne work to that time.

Re iinear linkage, Rothfels' paper in the curvent fienetics provides
an axcellent account. The sequence Ve~bacy~P-V)-L-T appears to be very

certainly linear, pobiing all the data. I am rather doubtful that the
association of M-Lac is actually a linkage, and the left end, Mal-S—Xyl-Mtl-M-B

1
ds still rather meesy, probably another chromosome. The elimination of
the Mai-region messes everyiaiing up there.

I would prefer that you not explicitly mention unpublished work on
the compatibility factors, although it wouldg of cours:, be quite fair
to keep it in mind in orienting the discussion. The whole thing should come
to a heed in the next year or so, but there is no way of telling just how it
will come out. It looks as if the polarity of the, compatibility factors
(F+:F~) detarmines which chromosome will be diminished forvMal..

I've been in close correspondence with Hayes about the possibility of

page in BE. coli recombination: he seema to be raady to retract the idea
althgether. I think you may perhaps have overemphasized it. The question of

the relationship of transformations or transduction to sexuality is also
brewing. My own feeling is that they are not so far apart: that transducing
factors are chromosome fragments of lesser or greater size that get into
donee celi, and are Incorporated into its chromosomes. My views are summarized
in the enclosed few pages (from a draft of a review: Cell genetigs and hereditary
syblosis, going to Physiol. Rev. may I have then back when you're through).
Would you care to have me look brifely at your chapter X?

Concerning prevalence of fertile strains, we have 50 now, from about 2000 teste.
There are probably more that were undetected because the tester, W-1177 1s F-,
but not, say, more than twice as many.

C.H. Browning probably deserwee credit daw first conceiving a sciective
test of recombination: J. Path. Bact. 12:166,1908.

Sincerely,
t Joshia Lederberg