Yale University New Haven, Connecticut 06510 
SCHOOL OF MEDICINE 
3 33 Cedar Street 
Department of Laboratory Medicine 
December 20, 1979 
Dr. Donald S. Frederickson 
Director - National Institutes of Health 
Bethesda, Maryland 20205 
Dear Dr. Frederickson: 
I am a member of the Biologic Safety Committee at Yale University and 
in that capacity have been involved in evaluating recombinant DNA re- 
search at Yale for the past several years. 
I strongly support the proposed change in the recombinant DNA guide- 
lines that will allow experiments using E. col i K- 12 to be done under 
the conditions outlined in the new Section III-O, page 69 218. Our 
institution and committee has had considerable experience with recom- 
binant DNA research and in particular with experiments concerning E. 
col i K- 1 2 . We have seen no evidence of potential hazard with this 
system and there has been no evidence that K- 12 is a potential path- 
ogen for transmission of vectors to other hosts. Clearly it is 
appropriate and safe to lower containment levels for K- 12 experiments 
and I urge that the new guidelines and in particular Section III-O 
be accepted. 
Sincerely, 
Professor, Laboratory Medicine 
JRB : tmm 
[ 559 ] 
