HARVARD UNIVERSITY 
The Biological Laboratories 
16 Divinity Avenue 
Cambridge, Massachusetts 02138 
December 14, 1979 
Dr. Donald Fredrickson, Director 
National Institutes of Health, 
Bethesda, Md. 20205 
Dear Dr. Fredrickson j 
I am writing you to express my approval of the proposed new 
guidelines for recombinant DNA research, I am especially enthusiastic 
about the proposed downgrading of containment requirements for experi- 
ments involving most coll K12 host-vector systems. 
As one who has spent nearly 50 years working with pathogenic 
bacteria, a good many of which were spent teaching medical bacteriology 
to students at New York University College of Medicine | as one who was 
a member of the CommlsjJ-on on Immunization of the AFEB for many years and 
is presently a consultant for USAMRIID at Fort Detrick, I have found it 
difficult to understand the present stringent requirements placed on 
working with E. coli K12 which I consider to be non pathogenic. 
It seems to me that there can no longer be any doubt that 
re combi national events axe constantly taking place in nature including 
in the intestinal tract of man. It is my guess that during the many 
thousands of years of daily recombinational events, an occasional one 
has, by chance, led to the acquisition of pathogenic properties. This 
would explain how many of the familiar pathogenic bacteria acquired 
the ability to cause disease. The chances that E.coli K12 might 
become pathogenic either by accident or design so as to create a 
danger thrpugh laboratory experimentation seems to me to be impossibly 
remote . 
Sincerely yours, 
cLTr, 
oJr\&L- \ ' 
A .M.PappenheLmer Jr. 
Professor of Biology (Emeritus) 
AMP/amp 
[ 487 ] 
