APR 29 1969

UNIVERSITY OF COLORADO

BOULDER, COLORADO 80302

DEPARTMENT OF CHEMISTRY

April 24, 1969

Professor Joshua Lederberg
Department of Genetics

Stanford University Medical Center
Stanford, California 94305

Dear Professor Lederberg:

Your letter of April 14 has only just reached me, having
been forwarded to this address from Yale. I can answer it in
part with some of the enclosed reprints. These include a report
on some measurements of terrestial C!"*0, and studies on reaction
of atomic carbon with inorganic molecules. I also send a review
on carbon atom reactions with organic molecules. (We have pub-
lished quite a few papers in the latter area, but the review will
probably provide all the information you want).

Your interest in carbon monoxide "metabolism" has started
me thinking again about some ideas which arose from this old
work of ours. The hypothesis involved is highly speculative
and since my main interest is in the nature of simple chemical
reaction, I haven't done much with it. However the few people to
whom I've mentioned it, including Willard Libby and Charles Barth,
could tell me of no obvious fallacy.

ofiy9 370M

The idea is simply that on CO, rich planets, like Mars, the
life cycle is likely to be based on the metabolic oxidation of
carbon monoxide. Solar UV radiation dissociates C0Q>.

CO, + CO + 0
0O+0+M-+ 0, + M

Reoxidation of CO to COz will then occur in a living organism.

As mentioned in my article, as cited by you, metabolism of
CO is possible: that is just what B. Oligocarbophilus does.
Moreover, and this is the critical point, the chemical machinery
necessary to extract metabolic energy from the oxidation of CO
should be capable of being much simpler than that for photosynthesis.
That would suggest that this metabolic cycle might be a primitive
precursor to the photosynthetic cycle. Conceivably when the
atmosphere of earth was rich in CO, rather than 02, terrestrial
life also might then have developed through a CO energy cycle.
Another advantage of the CO cycle to primitive life is that
jt means that the organism can stay out of direct sunlight. This
could be quite helpful as chemical combinations which would be
unstable with respect to solar photolysis could be employed.

If this hypothesis were correct then it would provide the
solution to a rather vexing problem. As I mentioned, citing
Bates, in my 1960 article, it is difficult to conceive of a suf-
ficiently rapid way to recombine CO and 0, on ,eangh, The same
problem seems to exist in regard to the Martian, atmosphere. The
rate of photolysis of CO, on Mars by light of wavelength less
than 1700 A is substantial. No good "inorganic" recombination
mechanism has been proposed. Why then is the steady state not
predominantly CO and 0, rather than C02?

The main drawback of the CO cycle is that it would make use
of onlyca small fraction of solar radiant energy (that part at
< 1700 A). While it might, therefore be appropriate for primi-
tive life forms, it should be overwhelmed by photosynthesis as
conditions permit and the more sophisticated chemical machinery
necessary evolves.

I would be most interested in hearing of your views on this
idea.

Sincerely,

Pils Blffpors,

Richard Wolfgang
Professor of Chemistry

P. S. Please address me as above until June 15
Enclosures

cc: Willard Libby
Charles Barth

RW:cl