112 Ransom Rd.,
Falmouth, MA O2540.
(508) 548-8903 (until Sept. 4).

Aug. 26, 1989.

Dr. Thomas D. Brock,
1550 Linden Dr.,
Madison, WI S3706.

Dear Tom,

Enclosed are the pages with corrections from the rest of your ms.
In general, it seems to me that you are not as close to the more
molecular, later material as to the earlier developments, and

SO you will find more suggestions than in the first batch. If I
may take the liberty of suggesting something of mine to read (in
addition to the reprints that I sent), the micro. text of which I
am a coauthor has a good bit of history, and you might find the
chapters on protein synthesis and on regulation, in e/3,
interesting; in a few places my interpretation differs from yours.

My largest general criticism is that Avery is undervalued.

Your postponing of transformation until after mating and
transduction results in diminishing the importance of his
discovery; and when you propose that transformation really
contributed little to the advance of bact. genetics you fail to
distinguish the importance of discovering the role of DNA from
the limitations of the technique far further exploration. The
fact that Avery had a strong aversion to speculating doesn’t mean
that he was really floundering or had no idea of the possible
implications for genetics. The main reason his work didn’t have
the impact of Watson and Crick is that it didn't suggest a
mechanism far gene function, nor did it automatically lead to a
broad range of expts., as their discovery did. Perhaps the
surprising thing is that his discovery didn’t stimulate more
people to get into studying the biochemistry of DNA -- the gap
between the biochemistry and the genetics must have seemed
insuperable.

Nevertheless, the smart people, some of whom you quote, rapidly
recognized the significance of identifying the material of
heredity. It was clearly what led Josh to quit med school and
seek the same in a more amenable organism. You give Hershey and
Chase a great deal of credit for making the role of DNA credible,
but even before that the work of Taylor and of Hotchkiss ~~ which
must be considered an extension of Avery’s work, in the same lab
~~ had made it clear that transformation was not a peculiarity of
type specificity but could be carried out with any identifiable
gene. The Hershey-Chase expt. was definitely confirmatory, and
quantitatively far cruder: it seemed so important only

because of the reluctance of the phage people to concede that
their logical approach had been upstaged by accident by a group
of medical bacteriologists. If the H-C expt. had not been done it
would have had little impact on the acceptance of the importance
of DNA, for within a year the Watson and Crick discovery would
have clinched it for even the most extreme skeptics. I find it a
bit odd for you to ask what would have happened without
transformation, rather than asking what would have happened w/o
Hershey and Chase.

Incidentally, since you enjoy digging out inadequately recognized
priority in other cases, I would think it worthwhile to discuss
why Avery's discovery didn’t lead to a Nobel Prize, though he
lived for 11 more years. McCarty’s book discusses Mirsky’s
unfortunate role dispassionately, and I discuss additional
factors in the BioEssays reprint that I sent you. I might add
that in my opinion Avery should be credited with initiating
bacterial genetics as well as molecular genetics, since he
provided the essential breakthrough of gene transfer. I think
you focus too much on the fact that the 1944 paper didn’t bring
this out clearly. Before then, what was reported about
transformation had no hint of being related to genetics: the 1944
paper now made that connection reasonable, even though it was
suggested only tentatively; and the fact that the strengthening
of the evidence for gene transfer came gradually rather than
dramatically does.not diminish its importance (again, consider
the springboard for Josh's work). On the whole, I think you give
Griffith's confused interpretation more detailed attention than
it deserves, relative to Avery.

IT would like to see a little discussion of the strong parallel
between transformation and generalized transduction (both
requiring double exchange with part of the introduced fragment),
compared with the several techniques for adding genes in a
replicon. Transformation led to the discovery that plasmids and
naked phage DNA also could be introduced, inefficiently, by a
Similar process, and so it was revived as an important techni que
by the recomb. DNA revolution. Terminology here is not uniforms
in our text we decided to use transfection not only for phage DNA
but for an intact plasmid, and transformation for introducing a
fragment of naked DNA.

Iwas surprised not to see more on plasmids; their importance and
their nature were well recognized before the time when you draw
the book to a close. At least a section on the resistance
plasmids would seem in order.

Two additional points about transformation. It might be
appropriate to nate that in Haemophilus the uptake of DNA is

much more specific than in —&. coli, and the two organisms also
differ in how they treat the strands. This topic could be linked
to a discussion of how transformation appeared at first to be an
artefact (i.e. DNA creeping into a rare, damaged cell) but it
turned out to be an evolved mechanism, since it has been shown
to involve specific enzymes.

In the discussion of Lysogeny there could be more emphasis on the
importance of recognizing that immunity is not an additional
consequence of lysogenization, as it first appeared to be:

fa
instead, the same mechanism keeps both the prophage and any
entering phage from initiating vegetative multiplication.

The discovery of transduction involved a bit of serendipity that
is not widely recognized and might be worth noting. Moving fram
E. coli to Salmonella, Lederberg and Zinder continued to use
double auxotrophs to eliminate the background of reversion to
prototrophy, but they soon found that the process in this
organism was usually limited to transferring one gene. If you
look back at their paper you will find that they started with a
double auxotroph for Phe and Tyr, assuming that these were
independent mutations. But this was almost certainly a single,
leaky mutation in the common aromatic pathway, for I had found
that as mutants in this pathway turned up with increasing
leakiness they lost successively the requirement for p-
hydroxybenzoate (discovered later), FAB, and Trp; the leakiest
were doubles for Phe + Tyr. The irony is that if L & Z had
started with an honest double mutation they might never have
discovered transduction!

Incidentally, I’m not sure that the picture of how transduction
works, with an agent that is filtrable but cauld not be detected
in the filtrate of either partner, comes across. The recipient
carries the prophage and rarely releases infectious particles;
when these infect the non-immune donor they give rise to a burst
of phage; and these particles, returning to the recipient,
accasionally transduce it (because immunity to reinfection does
not prevent mechanical introduction of the DNA). Also, in
discussing lysogenization I’m not sure you make it clear that a
phage infecting an indicator strain initially causes vegetative
multiplication in most cells, as in zygotic induction, while the
rare survivors have become lysogenized and immune.

Finally, I’m attaching a possible footnote, on a piece of history
that may be too obscure for you to feel appropriate to include;
but on rereading my paper in the Henry Ford Symp. I think I had
the problem pretty well figured out; Monod was then still a bit
ambivalent, as you could find in the Disc. on p. 47. Monod‘s
running away with all the credit is very similar to the
overshadowed Vogel discovery of repression, which has intrigued
you. Incidentally, Vogel worked in my lab, where I had begun to
get interested in regulation, and we first reported on repression
tagether, in an abstract. I foolishly did not pursue it further
because biosynthetic pathways were still so profitable.

I hope you find my comments helpful. Incidentally, because of
one late chapter the next ed. of the Davis et al. text will
unfortunately be too late for classes starting this fall. The
publication date is now set at Oct. 15.

Sincerely,

Bernard D. Davis

ted
a

Possible footnote on permease:

Bernard Davis has provided the following:

Before Cohen and Monod began to work on B-galactoside uptake
I had observed that Aerobacter auxotrophs for glutamate, which
were blocked in citrate synthetase, could use citrate instead of
glutamate in the absence of glucose but not under the usual
conditions of testing, i.e. aerobic growth in the presence of
glucose. Since the enzymes for using citrate were constitutive
it seemed evident that the variable response of the auxotroph
revealed induction of the formation of a transport system, and
its repression, like that of B-galactosidase, by glucose.

Howard Green,-a post-doctoral fellow whom I encouraged to
pursue this lead, then showed that wild-type Aerobacter could
metabolize radioactively labeled citrate, after a lag, in the
absence of glucose but not in its presence: a typical diauxic
response. The conclusion seemed inescapable that the organism
formed an inducible and repressible transport system for citrate.

I reported these findings shartly thereafter at the Henry Ford
Hospital Symposium (ref.) It may be difficult today to imagine
how hard it then seemed to accept the idea of a variety of
specific transport systems in the tiny bacterial cell. At that
time Erampits was having difficulty convincing microbial
biochemists, and even Krebs, of the existence of the Erebs
tricarboxylic acid cycle in E. coli, because the ability of
extracts to carry out all its reactions left unexplained the
inability of intact cells to utilize citrate. My proposal of
inductive changes in a morphological entity such as a membrane

would seem even more radical, and Dr. Green refused to risk his
reputation, as a beginning scientist, by attaching his name to
this conclusion; I could therefore only acknowledge his
contribution in a footnote to the data.

Monod (with whom I had worked for a few months) came through
New York on the way to the same symposium and he told me of his

discovery, with Georges Cohen, that &. coli could concentrate a

non-metabolizable B-galactoside. In their initial, brief
publication in the C. R. Soc. Biol. they did not choose between
active concentration, which seemed too much to expect of a tiny
bacterium, and stoichiometric attachment to induced "hooks" in
the cell. Moned favored the latter, and I tried hard, without
success, to convince him that the answer had to be a transport
system. (Pappenheimer, in whose apartment we met, eventually
pushed me out the door sa they could resume wark on a joint
manuscript.)

At the symposium in Detroit I presented my strong
conclusion, while Moned presented an ambivalent interpretation of
his data. However, in the later, published version he had
become mare receptive to the idea of active transport.
Subsequently, as this book describes, he and Georges went on to
an elegant analysis of their system. Though I continued to work
on citrate for a while this work was not fruitful, for it lacked
& non-metabolizable analog that could be actively transported,
and there was mo background of genetic studies in Aerobaacter.
Nevertheless, when Monod gave the Dunham Lectures three years
later at Harvard, as a quest of the department to which I had

meanwhile moved, I found it painful that he devoted a lecture to

i

\

/
"permeases” without mentioning my work on citrate. As in other

episodes described in this book, he did not share important

discoveries willingly.

Reference:

Davis, Bernard D. Relations between enzymes and permeability

{membrane transport) in bacteria. pp. S09-S22 in Gaebler, O. H.
(editor), Enzymes as Units of Biological Structure and Function

(Henry Ford Hospital Symposium). Academic Press, New York.

Tom: if you find this interesting but too detailed please feel

free to use the material as you wish. Tf you use it as a direct

quote I suppose I ought to see any altered version.