STANFORD UNIVERSITY MEDICAL CENTER 
STANFORD, CALIFORNIA 94305 
DEPARTMENT OF BIOCHEMISTRY 
Area Code 415 
497-6161 
Stanford University School of Medicine 
September 14, 1979 
Dr. Donald Fredrickson, Director 
National Institutes of Health 
Building 1, Room 124 
Bethesda, Maryland 20205 
Dear Dr. Fredrickson: 
Dr. Rowe asked me to bring you up-to-date on the stability and likely survival 
or organisms containing recombinant DNA. We have worked with E. coli K12 cells 
containing a very large number of different recombinant DNA's. We have worked 
with both cells containing plasmids and derivatives of bacteriophage A. We have 
consistently found that great care must be exercised during experimentation and 
for long term storage, that our K12 cells still contain the recombinant DNA. 
We have found that during long term storage and during growth, using many classi- 
cal methods, that E. coli K12 strains lose the recombinant DNA. In many cases, 
rather elaborate schemes have been invoked to assure that our cell lines will 
maintain the recombinant DNA. We now store our cells in dimethyl sulfoxide at 
-70°C. Considering the loss of recombinant DNA from these micro-organisms during 
ideal growth conditions and considering the general lack of competition with 
wild type cells, I cannot conceive that E. coli K12 containing recombinant DNA 
could find an ecological niche outside of the laboratory. We have conducted 
rather extensive competition studies comparing the growth of bacteriophage A 
containing various recombinant DNA's to that of wild type A. Results of some 
of these studies are reported in Science, Vol. 196, p. 212-215. Our general con- 
clusion is that inserting foreign DNA into bacteriophage A decreases its growth 
potential. We have not found, as of yet, an exception to this conclusion. I 
strongly support the recent RAC decision to exempt all recombinant DNA experi- 
ments conducted in E. coli K12. 
Sincerely 
Ronald W. Davis 
RWD/ ras 
cc: Dr. Wallace Rowe 
Dr. William Gartland, Jr 
1323J 
