March 5, 1955
(Friday)

Dear Bruce:

Tam sorry that I do not have more to report to you in this letter.
Robert Wright, one of my students here in the lab. and a wonderful
perscn in every way had a terrible auto aecident Monday, with severe
cranic-cersbral injury. He has been unconscious since then, and all of
us have been rather more concernedywith that than anything else around
the lab. It would be difficult to convey our feelings about it.

However, I did want to communicate something to you about the
clone plating experiments. I have been using SW-534 —x 553, as being
the most prolific, with the fewdest interfering waarms. Individual
motile initials (about 3 hours) have been picked to 1/2 a1 broth, allowed
to grow to clones of sbout ICO, an’ these then plated im as pour plates
in motility agar. This gdéves beaktiful pictures of trails, dot influenced.
by mtebolite gradients, ete.. I have also plated larger numbers of
initials collected together, and without post-incubation, and these give
about 1/7 trails per viable colony with quite lerger s auples.

So far about a ddzen clones with traila have néen found, in each case
singly. I was exercised for a time abovt fairly nuserous "minor trails"
which appeared especially after 48 hours incubation, but these have proved
to be of spontaneous origin. I.E. SW-553 (or rather the reisolate SW967)
gives these by itself. And surely enough, these cultures do engender a
very small number of motile individuals. I have followed a few clones
from these. Motility is quite weak and irregular. Most of the clones in
which motility persisted at all were tinicatenate, but one or two at least
were distinctly di-catenate, though persistent chains were not developed.
Ordinary platings of SW-967 have not shown the spontaneous minor ‘traiis,
possibly owing to inhibitions by the excess non-mctile individuals of

,  sgurfece platings.
transduction
If thexu clones continue to give the same picture of isolated occurren
ce of trails, I igaxk shall have to abandon my opposition to the two levels
of mxuna esatenation, but I shall have to switch over to —541 or —=x 666
to finish up. There are some photographs of these pour platings in the
making and I will send some copies when I have them printed up.

[ALAIN

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