November 25, 1953

Dr, °. D, Skaar
Biological Laboratory
Cold Spring Harbor
Long Island, New York

Dear Dave:

Your breesy, optimistic and informative letter was most
welcome, I especially appreciate how promptly you replied to
my questions on the motility of line 28, This has been a
rather puzzling matter, but I think I now understand at least
some of the discrepancies, The original line 28, that is,
W1258, the culture that was used in your experiments, is
certainly motile now as it was then, I checked this only
since receiving your letter, For the purposes of crossing
and other reasons, however, we have been using in place of
W1L258 a culture described line 208A, 268A is evidently not
motile, It differs from the original W1258 also in being
typically prototrophic and resistant to streptomycin, We
are investigating the other properties of 23 and 234 in order
to come to some sort of definite decision as to their genetic
relationship, 1258, original, characteristically grouse very
poorly, even on complete media, I think this must be the ex-
planation for your comment four, paragraph three,

It is unfortunate that we have no rood quantitative method
of estimating motility. I have often noticed among various
Salmonella cultures that there might be very little correlation
between obviou: microscopic motility anc the ability to swarm
through soft agar, For example, Salmonella abortus-equi is
generally very motile indeed by microscopic examination and
yet scarcely swarms at all in motility azar,

In a way I am sorry to hear that you are roing into come
petition with Cavalli on this matter of B by K12 crosses, I
assume, however, that Szybalski cleared this with Cavalli when
he visited him at Rome, It is very difficult for me to make any
comment about your 3 by K12 results until I get a little bit more
definite information from you. For one of your experiments, how-~
ever, I am sending you #1305. This is a multiple auxotroph m-t-l-
P. D, Skagr--page 2 November 25, 1953

from line 1. We had found it useful here a8 a source of the F+ agent
which was not effectively crossable with either of the other main
crossable lines, but I think you may have some difficulty in recover-
ing and then proving new mutations in B which might be allelic with
t~ and l- in line 1, As soon as I can eet around to it, I will send
you the cultures that you asked for, As you know, we do not have
very many singly deficient stocks, and for she purposes of your
reverse mutation studies, you probably would be just as well off
to make your own mtants, I will, however, dig out what we do have,
I am afraid we cannot help you out on your first request for a
multiple marker strain from Y1O that will be sensitive to Tl,
Unfortunately, this was just about the first marker put in before
all of the others, I can, however, give you Wl which is Y19
lace mal- *

I did not realize that you had had an opportunity to file
the retirement form, Other people who have been here had managed
to over-look this detail, I guess that's all for now, Dave, I
am still waiting to hear from you concerning a long over-due report,

Yours sincerely,

Joshua Lederberg
JL/gw