October 22, 1951.

Dr. M. Doudoroff,
Department cf Bacterlology
University of Califorbia
Berkeley 4, California.

Dear Miket

As you know, Roger spent the weekend with us, and we had a fine time.
One experiment didn't work, however, -- we tried to test Roger's pet idea
about the basis,of non-oxidising S™ mutants in coli. Unfortunately, none
of our 3” mutants ageeddrwith Unbreit's description of cultures whose growth
was not improved by aeration.

I hope you enjoy "Velvet Bacterlology"~— Roger told me he was suggesting
some class experiments with it. Streptomycin resistance of P. flucrescens
ought to work rather well, but I haven't tried this particular system. I'll
be interested to hear how it works out.

Thie letter is mainly to ask about the prograss of your work with the
block to glucose-utilization in the coli mutants. Roger mentioned that you
had pretty well ruled out hexokinase as the key step, but had given up the
problem for the moment. I would appreciate it very much if you could send
a summary of the experiments. The Lac,- mtant is an important example of
pleiotropic gene effects, and it see7& unfortunate to have to be sloppy about
saying "no lactase, amylomal tase, "glucozymase? 727?" ,

If I could ask a second favor, could you send me back a culturs of W-108
(the original Lac3-) if you still have it? We're putting away our culture
collection now, and I have this stoek only dn one pessibly doubtful lyophil
tube. I'm doing some expsriments on crossing glucose x galactcse~-negatives
to get some genetic evidanee on the role of the hydrolytic galactosidase in
lactose fermentation. There seems to be another case of "direct fermentation"
brewing, but I'll have to look into the adaptations more closely. But I won't
be too surprised if the extracted galactosidase is partly an art®8act, such
that its intracellular function 1s less simple. ‘The same seems to be pretty
clear for amylomaltase, from your comparison of the complete utilization of
maltose with the hemiplegic behavior of the dried prens,

Fe sure to get Roger to narrate a discussion we had with one of our
local leading lights on the possibilities of a genetics of acthnomycetes. .

Sincerely,

Joshua Lederberg