Ne oartment of Shenl

Shelsen Tollege of Jac ance and
AM Teminglo cs
; Shelsea, London, 3.7.‘

ingland,

 

end April, 1958.

rofessor Lederberg,

for not
issing

hank you for your ktter of 24th February. Ple
replying earlier, but I have bem eiving the miter s
it with my associates.

 

 

T realise fully thet much work has been published in support of

 
 

moiifvication theory rather than a process of natural selection. TI preswmac that
some of the work to which you refer is that of Hinshelxood and his Cxforca School,
As I received my early training in that school I suppose 7 am sliantly ops judicedt

Your interpretation of the data in Fig.8 are correct, namely thas curving the
lag chase (up to about 1800 minutes) we never detected any cells “th low eobility
vyaluzs. As soon as cell division occurred then the newly formed cells hed the low
mobility value. The cells with the hieh mobility values represent the *raction which
vias dead at the end of the lag phase (we carried out viability measurements during
the lag phase). This proportion decreases during the logarithmic growth pnase, and
in some instances we detected 1 or 2 cells with high mobility values in che
stationary phase. I should point out that the cells were stained with crystal
violet which could not be washed off,.thesmount, however, was so small that this
did not cause the lowered mobility value. Generally it should be possibile to
discriminate a minute proportion of organisms with a different mobility to the
bulk. .In this case it is impossible to make a random selection in the observation
chamber since the cells with low mobilities are very small, compared with those of
high mobility. This is a very unfortunate situation.

I presume that from whe standpoint of the theory of natural selection you
would expect 1 cell in 10°, or thereabouts, in the normal strain to have a low
mobility value. I have calculated that to explain the graph (Fig.8) on this theory
we sould have to postulate 1 organism in 10!" with a low mobility value. Ve have
no chance of detecting this. During the 8 years we have been working on this
organism we have never recorded such a low mobility value for cells in a normal
culture. As far as the theory of natural selection is concerned I should have
thought that adaptation to a bacteriostatic agent should occur relatively quickly.
Hinshelwood and co-workers find that adaptation to sulphonamides, as measured by
decrease of lag and increase in growth rate to normal, is a very slow process.
Perhaps I am wrong in this concept. ‘

Recently we have been using your method to: obtain protoplasts from Aerobacter
‘aerogenes and so far can report good success. When we have,established the.
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