Débarfnfent of Genetic:
University of Wisconsin
Matileon 6, Wisconsin

June 10, 1955

Dr. Nils Aall Barricelli
Matematisk Institutt
Blindem, Oslo, Norway

Dear Dr. Barricelli:
Thank you for your reprint from Acta Biotheoretica.

I would comment that I find myself, on the whole, ehtirely
sympathétic with your point of view, though my position is
perhaps not so advanced as your own. At least, the concept of
hereditary symbiosis should be considered as at least one of
several, not necessarily mutually exclusive approaches to the
nature of the organism and the origin of life.

For this purpose, however, I do not find it necessary to as-
sume that the ganes of any contemporargnous organism ase so devoid
of integrated structure as you seem to propose, and I doubt very
mach whether we have left today any certain examples of independent,

© isolated "single genes".

As to your interpretation of crossbreeding in bacteria, I would
also submit a more eclectic approach. The evidence that recombination
in E. coli is sexual cannot be so lightly dismissed— if by sexual
you mean the fusion of entire nuclei (i.e. genomes). Lately, we
have evidence that this is accomplished not by the fusion of entire
cells (as in the algae) but rather by temporary conjugation (as in
Paramecium). We perhaps arrive at a question of definitions-- your
genophore here becomes what I would call the gametic nucleus, but the
point is that the latter is an intact genome, not a fragment as in
the transduction system. The latter is, moreover, as you know mediated
by sub-cellular agents (phage or DNA) in distinction to the K-12 xsoomkt
sexual system. But I do not see why your theory should exclude the
possibility of a fully evolved sexual system, as well as the more
fragmentary techniques of genetic recombination.

You will, I think be interested in a recent progress report from
Hershey's laboratory (Carnegie Inst. Yrbk. 53: p.216) which records
experiments to test the effect of the host bacterium on the quality
of the phage progeny, as well as in references(in reprints {sent under
separate cover) to lysogenic conversions. As concerns the interpre&a-
tion of transductions in Salmonhlla, I think the phage-genes in this
fase mist be considered as distinét from those of the host bac terium,
since the transducing competence of any given crop of phage is deter-
r mined entirely by the genotype of its most recent host. This distinction
does not hold for the lysogenic conversions, which are more a propos
your argument. The reconciliation that I make is that the phage nucleus
is homologous with part of the bacterial nucleus. For the most part,
the association between the toc is adventitious (in Salmonella trans-
duction) but not in the lysogenic conversions. The Gal~Lp system (see
reprints) is intermediats.

May I inquire whether your interest in
consider working sxperimentally with these materials?

I would be iniebted,to you for reprints of your other papers. I would also
be intessed in any clues as to how I might obtain access to the other publi-
cations (or perhaps microfilmm of them) that you quoted in re "symbiogenesis",
(Keller; Kozo-Poliansky). I have marked reference numbers in the reprint
of my review (Cell Genetics and Hereditary Symbiosis) which you may find es-
pecially pertinent to the general discussions.

Yours sincerely,

Joshua Lederberg
‘Professor of Genetics