Agricultural Research and Development Center 
WOOSTER, OHIO 44691 
TELEPHONE (216) 264-1021 
DEPARTMENT OF 
PLANT PATHOLOGY 
September 19, 1978 
Mr. Richard Riseberg 
DHEW Office of General Consul 
National Institutes of Health 
Bldg. 31, Room 2B50 
Bethesda, MD 20014 
Dear Mr. Riseberg: 
When I testified at the public bearing on the Proposed 
Revised Guidelines for Recombinant DNA Research on September 
15, I submitted only a summary of my comments. Enclosed you 
will find 20 copies of my complete statement for your use. 
I have two additional comments on the revised guidelines 
concerning the proposed list of "gene exchangers". First, crown 
gall caused by Agrobacterium tumefaciens has become a popular 
model system for many molecular biologists studying cancer, gene 
transfer between prokaryotes and eukaryotes, and plant cell 
differentiation. The ommission of Agrobacterium radiobacter from 
the list of "gene exchangers" is serious because this species is an 
avirulent form of A. tumefaciens and is distinguished from it solely 
on the basis of tumorigenicity . Thus, an A. tumefaciens strain which 
has lost its virulence plasmid could be classified as A. radiobacter . 
Second, I forsee that there will be a need to add the genus Xanthomonas 
to the list of exchangers after more work has been done on plasmid 
exchange between it and P. aeruginosa and I[. coli . It would be 
helpful, therefore, if the guidelines were more specific on what 
critera must be satisfied to place an organism on the "exchanger" 
list . 
[A-172] 
