.^CTIC^ 
C 7he Connecticut ‘Agricultural ‘Experiment Station 
123 HUNTINGTON STREET BOX 1106 NEW HAVEN. CONN. 06S04 (203) 787-7421 
Founded 1875 Putting science to work for society 
18 November 1977 
Dr. Donald S. Fredrickson 
Dept. of Health, Education & Welfare 
National Institutes of Health 
Bethesda, Maryland 20014 
Dear Dr. Frederickson : 
Two aspects of the revised guidelines are of some concern to plant 
scientists : 
(i) The introduction refers to the fact that the Guidelines "pertain 
only to novel recombinant DNAs...from different species not known to ex- 
change chromosomal DNA by natural physiological processes". They go on to 
refer to a list of combinations of DNAs not considered novel. I believe 
that the word "chromosomal" should be eliminated. Prokaryotes that ex- 
change plasmid DNA surely also exchange chromosomal DNA that happens to be 
part of the plasmid. I do not see the need for formal proof of this for 
each pair to be included in a list. 
Agrobacterium tumefaciens offers one of the most promising systems 
for introducing foreign DNA into plants. It exchanges plasmids with E. coli , 
Rhizobium and other gram-negative bacteria. I would interpret the revised 
guidelines to list A. tumefaciens x E. coli , and A. tumefaciens x R. trifolii 
as exchangers. This would allow important work with J2. coli K12 clones of 
A. tumefaciens plasmid DNA to proceed without any restriction instead of P2 + 
EK2 presently required. 
However if a less liberal interpretation requires documentation of 
exchange of chromosomal DNA between the strains to be employed then, in the 
meantime, containment will be severely increased as explained in my second 
point. 
(ii) The revised guidelines require P2 + EK2 or P3 + EK1 for non-exchang- 
ing bacteria with DNAs that are not extensively characterised. However, 
plant pathogens are equated with Class 2 and require P3 + EK2 (P49602 Col. 1. 
line 29). This is a mistake. Although there is still no risk classification 
for plant pathogens beyond endemic vs. exotic species there is little reason 
to equate plant pathogenic bacteria with class 2 agents. American scientists 
working with A. tumefaciens for example would be greatly hampered by P3 + EK2. 
I suggest that the words "and plant pathogens" be deleted on this line. This 
[Appendix A — 76] 
