STANFORD UNIVERSITY MEDICAL CENTER 
DEPARTMENT OF GENETICS 
December 11, 1979 
Dr. Donald Frederickson 
Director, National Institutes of Health 
Bethesda, MD 20014 
Dear Don: 
I am writing in response to your request for additional public 
comment on the recommendation of the Recombinant DNA Advisory Committee 
regarding experiments involving E. coli host-vector systems. I strongly 
support the proposal to revise the Guidelines to exempt from the 
Guidelines prior review procedures and to specify Pi containment 
conditions for all recombinant DNA experiments using E. coli K12 hosts 
(not containing conjugative plasmids or lysogenic for generalized 
transducing phages) with lambda or lambdoid bacteriophage nonconjugative 
plasmid vectors. 
As I have previously written, there is no indication that the cloning 
of DNA in E. coli K12 poses any hazard that warrants precautions beyond 
reliance on standard microbiological procedures, and in fact experience 
indicates that recombinant DNA methods provide increased safety for work 
with genetic material that does encode hazardous products. Since there 
is no reason to believe there are special hazards in the experiments 
proposed for exemption, there would seem to be no need for a special 
administrative process to promote safety. Standard microbiological 
practices appear to be adequate for work with a variety of organisms 
capable of causing serious disease or environmental damage; if special 
regulations and enforced guidelines are not necessary to protect the 
public health and the environment from organisms that are known to be 
hazardous, they surely should not be necessary to deal with organisms 
that have given no indication of being hazardous at all. The 
continuation of special procedures for work involving cloning of DNA in 
E. coli K12 would be justified only if there were some valid reason for 
believing there are special hazards. 
I strongly urge you to approve the change recommended by the Advisory 
Committee. This change would place the biohazard issues in appropriate 
perspective for a major component of recombinant DNA work by relying on 
standard microbiological practices, rather than on special regulations, 
to promote biosafety. 
Sincerely yours 
Stanley N. Cohen 
Professor 
SNC : ps 
1442] 
DEPARTMENT OF GENETICS, STANFORD UNIVERSITY SCHOOL OF MEDICINE, STANFORD, CALIFORNIA 94305 • (415) 497-5052 
