October 17, 1950,

Dr. #ortimer P, Starr,
Department of Bacteriology,
University of California,
Davis, California.

Dear Yort:

I promised that I would =rite to you to attempt to axcite your enthusiasa
for the problem of genetic recombination in phytopathogenic bacteria -— and
this is it. I think that I did remember to send you a mimeographed copy
of an cutline of experdmental methods in the production of mutants. They
are all really quite simple and successful, particularly if you know the
general nutritional idiosynerasiees of the organism you are working with.

e techniques for identification of nutritional requiresents of mutants
are also included, but you could have written that chapter from your own
experience.

Under separate cover, I'll send you all of the other reprimts which I
can afford. Some of these are nearly exhausted, so I am going to make the
rather unusual request that you return those marke! ""lease return", at
your leisure, unless they will be of special use to you because of your
undertaking this kind of work.

The main leads which point to phytopathogens as likely material are the
papers of Braun and Elrod, J. Bacter. 52: 695-702 1946, and their predecessors
Stapp 194.2 and Stapp and Bortels 1931, cited there. From the general morpho-
logical descriptions, I suapect that Agrobacterium radiobacter would also
do as well or better. Do you know of other bacteria fn thkis group niich
form star~shaped clusters under experimentally reproducible conditions?

The genetiv investigation of these forms seems important on two grounds.
Piystly, we have a cytological picturs, already made, which points towards
the possibliity of sexual fusion, If this can be verified, it would be a
considerable step ahead of E, coli K-12 where only the genetic picture is
available. Secondly, recombination would allow an akalysis of the problem
of pathogenicity in, e.g., Agrobacterium tumefackens, and could throw eome
light in particular on the gradual attenuation of virulenee of this species
by prolonged cultigation on glycine medium. I think there {5 room for the
possibility that the virulence of this bacterium is partly determined by
a virus-like agent, but this can only be properly studied with genetically-
well-understood material.

It goes without saying that we enjoyed visiting the Starrs very much. I'm
only sorry that we did not have a chance to get together more frequently and
leisurely.

Sincerely,