9th July 195i
-Deat® Professor Lederberg, :
_ Thank you for your letter, I quite agree with your remark about
the possible prevalence of cross purposes. Among reprints which I am
sending you separately you will find one by A.A.Eddy on yeast and galact-
eke which describes behaviour quite different from what Baskett found
with D-arabinose and from what Dean and I have recently found with Bact.
coli mutabile and lactose. Moreover, Brenner, who has been working on
phage resistance here,finds very sharp contrasts between the phenomena
which he has observed (or confirmed) and the behaviour of aerobacter |
with.proflayvine,. We both felt that. much phage resistance is the result
- of a destructive mutation, though “the establishment of lysogenic
. systems I believe to be another example of the "gearing" of metabolic
systems. a ee ae
: I might explain that for a very long time my aim was to show chem-
ists that the machinery of living systems could be of interest to them.
That a cell should only gradually develop its capacity to attacy} a sugar
did not seem to me necessarily to have more evolutionary significance
than that hexane vapour and oxygen show a long induction period before
visible reaction sets in. I think I should still be surprised to find
that simple substrate adaptations were of great ultimate significance |
(except of course as clues to cell mechanism). I agree that resistant
forms are harder to judge. I feel pretty sure the mechanisms of ss
resistance are varied. To mention only one point ; proflavine resistant
cells of aerobacter take up more drug than normal forms, whereas
phage resistant coli. cells may not adsorb at all. ~
The strain of Bact. lactis aerogenes will be sent to you as soon
as it can be prepared for transport. As to the strain trained to
D-arabinose this may take a little time to culture. since we fe: not
normally preserve sub-strains of this type. The adaptation to
arabinose is pretty persistent after 5-16 passages in an ammonium
sulphate-phosphate medium with this carbon source. The lag in.a
liquid medium always lengthens by a few hours (as compared with the
initial days) out of contact with arabinose, or the plate lag by
perhaps half a day. .
ou raise a question about the paragraph on replication. The
2 x 10/ cells of the inoculum were not counted of course on the
resulting plate but inferred from a parallel roll-tube count on a
dilution. The statement that single colonies were visible on the plate
is, I am afraid, a little confusing and irrelevant. Reference to the
records shows that all that was meant was that the practically
confluent growth did show under magnification the kind of apbéarance
‘Whitch:4snewspaper photograph would show rather than the kind of
pellicle one gets with "spreaders" like B. subtilis.

Yours sincerely,
Cw NS. 1 fe, bbe od