PROJECT K: “THE COMPLETE SOLUTION
OF E. COLI’*

F. H.C. CRICKt

It is convenient to consider future developments in molecular biology
(in the widest sense) under three headings: (a) studies on cell components,
(b) studies on unicellular organisms, and (c) studies on multicellular
organisms. The latter, although of great importance, will not be dealt with
here. The division between cell components (which may come from any
sort of cell) and organisms is admittedly arbitrary and is only introduced
here to make the discussion easier. In practice, most work on complete
organisms is supplemented by studies on the components of that organism.

It is first necessary briefly to take stock of the present position. As far as
classical biochemistry is concerned, many enzyme reactions are known,
and for a minority of these the action of the pure enzyme is understood
in outline. For no case have the details of the enzymatic action been firmly
established in chemical terms. Within the field of molecular biology (in the
narrow sense) we now understand in outline the synthesis of the nucleic
acids and of proteins, their interrelation in the genetic code, and a little
about their control mechanisms. ,

It seems likely that future progress will take place in several broad areas:

1. The more detailed test-tube study of the structure and chemical
action of biological molecules (especially proteins). Typical of such studies
will be the detailed action of enzymes (already getting very close with the
solution by X-ray crystallography of the structure of several enzymes), the
way proteins fold themselves up (a backward field), the radiation damage
to molecules, especially to DNA, and many other topics. It is character-
istic of these studies that they involve the application of complicated and
advanced methods of physical chemistry to biological molecules, and often

* The idea arose in conversation with Dr. Sydney Brenner, who invented the title
“Project K” and whom I have to thank for useful discussions on the topic. This short
Paper was originally circulated in a European Molecular Biology Organisation (EMBO)
document [1] toward the end of 1967. It still seems to me to be an attractive scheme
for people of the right temperament, and since EMBO is now unlikely to take it up I
thought that it might be useful to give the idea wider publicity.

+t MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, England.

Perspectives in Biology and Medicine « Autumn 1973 | 67
require rather large amounts of (pure) material: We may also expect the
chemical synthesis of model compounds to play an important part.

2. The filling-in of the broad outlines already established, for example,
the biochemical mechanism of protein synthesis, the unwinding of DNA,
the mechanism of genetic recombination (which is probably related to
DNA repair mechanisms), and, on the classical biochemical side, the
exploration of more metabolic pathways and especially their interrela-
tionships.

3. Work on subjects of fundamental importance which are little studied
at the moment, for example, the structure and function of cell mem-
branes,! the mechanism of cell division, and the biochemistry of spore
formation.

4. The study of control mechanisms at all levels, in particular the inter-
relation of the known mechanisms, leading to an appreciation of the
economy and “design” of the cell.

5. The behaviour of natural cell populations and their population
genetics, leading to the consideration of the evolution of the cell.

The above discussion is necessarily sketchy, but it clearly brings out
three important points: (a) an enormous amount of work remains to be
done without ever going to multicellular organisms; (b) important prob-
lems exist at all levels of complexity; and (c) there is likely to be an in-
creasing demand for large amounts of pure cell components present in the
cell in rather small amounts. For these reasons, it seems certain that in
spite of the obvious opportunities awaiting the study of organisms having
many cells, a major effort will almost certainly continue to be applied to
single-cell organisms, in particular to bacteria.

The point of this paper is to argue that such work should be concen-
trated on one organism (probably Escherichia coli, K12) and that a case
exists for centralizing many aspects of such work in a “central laboratory.”

The major reasons for wanting to have the “complete solution” of a
bacterial cell have been listed above. In addition, there is the intellectual
satisfaction of having a single living cell “completely” explained. Of
course, it is unlikely that the work will ever be pushed to the point that
every possible detail about the cell is known. It does not seem very prob-
able, for example, that all the various proteins of the cell (which may
number several thousand) will all have their amino acid sequences and
stereochemical structure determined. By “complete” one means complete
in the intellectual sense, implying that nothing appears to remain which
further experiment could not easily explain using well-established facts
and ideas.

It is clear that if the cell is going to be considered as a well-integrated
chemical factory, information from many different laboratories will have

1 The understanding of cell membranes has advanced greatly since this was written.

68 | F.H.C.Crick + E.Coli
to be pooled. This might argue for a central laboratory to act as a focus
for such work, but there are additional reasons of a technical nature which
make the case even stronger.

In the first place, the technique of studying the action of a gene by pick-
ing up specific mutants of it is likely to continue to be widely used. Now
for a limited class of genes it is possible to devise special selective tech-
niques, but this cannot be done for the majority. For many genes, how-
ever, it is possible to produce “conditional lethal” mutants. These are
usually of two classes: (1) temperature-sensitive mutants, which grow at
one temperature but not at another, and (2) suppressible mutants. Un-
fortunately, when producing these mutants one cannot usually obtain
mutants of just the gene being considered, but mutants in many different
genes. These must then be screened to obtain the class of mutants in
which one is interested. The rest are usually discarded, which is clearly
a wasteful process. It would bea great advantage if such mutants were
characterized as far as possible so that they could be made available to
other workers who might wish to study them in more detail. A central
laboratory for producing mutants, and for receiving mutants from other
laboratories, which would then be classified, stored, and made available to
others would be an obvious help to everybody in the field.

Another reason for a central laboratory would be the production of cells
on a large scale. Again, at the present time the tendency is for each labo-
ratory to grow a large culture for one particular chemical component in
the cell and to discard the rest. This is wasteful and will become more so
as larger batches are needed in order to obtain sufficient supplies of the
rarer molecules in the cell. Whereas some growing could be done commer-
cially, this will not be enough in the long run, as large batches of special
mutants will eventually be required for certain pieces of work.

All this suggests that there is a case for a central laboratory to coordinate
and assist experimental work going on in many different places. It remains
to discuss the choice of a suitable organism. There is, of course, no rea-
son why eventually a central laboratory might not deal with several organ-
isms, or alternatively that several such laboratories be started, each with
its own special organism. However, in the first place it would seem sensible
to start with one only.

The obvious requirements are: (1) the organism should be reasonably
small to reduce the complexity of the problem; (2) it should be easy to
handle and able to grow on a relatively simple, defined medium; and (3)
the same strain should be used by most workers. Yeast is probably too big,
and has the complication that many different yeasts are in use (eg.,
“bakers’ yeast” and “brewers’ yeast”). It has the advantage, however, of
easily forming stable diploids. The pleuropneumonia-like organisms
(PPLO), though small, are difficult to handle and need a complicated

Perspectives in Biology and Medicine + Autumn 1973 | 69
growth medium. The obvious choice: is Escherichia coli (probably the
K12 strain for genetic reasons), but Bacillus subtilis and possibly Salmo-
nella would also have to be considered. The main point is that several
reasonably satisfactory organisms are already well known. The final choice
between them could be left open at this stage.

A central laboratory might well contain the following groups: (1)
a genetic group for developing new and rapid methods of genetic map-
ping and screening; (2) a group to develop instruments for the automation
of experiments; (3) a biochemical genetics group to produce, receive,
classify, and supply mutants of all possible genes; (4) a fractionation group
for developing more and better methods of fractionation; (5) a production
group for supplying very large batches of partly fractionated material; and
(6) a group to study control mechanisms and the general economy and de-
sign of the cell. To this could usefully be added various associate groups
and visiting workers studying areas of growing interest (such as mem-
branes or cell division), who would find the facilities provided by the rest
of the laboratory am attraction and who in turn would point out the
material most needed at any particular time.

Postscript: Since the above was written, some of the last-enumerated
suggestions have been taken up, in particular (3) and (5). However, as far
as I know, no one is at the moment trying to set up a central laboratory,
and the idea of making our knowledge of E. coli (say) as complete as
possible has not been announced by any group as their acknowledged
target.

REFERENCE

1. Proposal for a European laboratory of molecular biology. Document CEBM
68/31E, European Conference of Molecular Biology, November 1967.

THAT LITTLE GAMETE

Of all the spermatozoan in the sea
You my stout lad swam free;
How fortunate am I that you were me.

GeEorcE W. GILL

70 | F.H.C. Crick + E. Coli