5 . 
are convinced the ecological considerations concerning procaryotic hosts are 
more important than any possibilities of genetic modification, as far as 
reducing human health hazards. Our reasoning follows. 
The Woods Hole Guidelines of August spoke of an untested, EK-2 system 
where survival of host and vector would be lowered 10^ compared to wild type 
E_. col i . Suppose, and it is indeed a question, that such "disarmed" hosts 
and vectors can be constructed, so that survival potential in laboratory media 
and laboratory rats is lowered 10°, or even further. It is erroneous to 
believe tiiat the nominated "safe" host-vector systems insure "safe" experiments. 
Over the many years that these experiments will continue, there may very well be 
genetic exchange from the constructed "safe" host vectors to wild type vectors. 
This could occur on lab surfaces; it could occur in someone's body following 
inhalation or ingestion and preceding death of the crippled original host, or in s 
systems if the crippled host survives to be excreted; it could occur in "safe" 
cultures which are contaminated. Perhaps, above all else, prolonged survival 
and genetic exchange could occur in special natural environmental conditions 
sometimes encountered by E_. col i , that we in our ignorance of this bacterium's 
specialized habitats, know nothing about. 
We can focus momentarily, for an example, on contamination by both wild 
type E. coVi_ and wild type vectors of "safe" cultures. Bacterial and phage 
contaminations of lab cultures are very common occurrences in microbiological 
labs despite investigators taking extensive precautions to avoid them. Suppose 
the initial culture of "safe" host is contaminated with wild type host at the 
time the recombinant DNA molecules are introduced. Then the wild type E. col_i_ 
may pick up the recombinant DNA and replicate it right from the start. Phage 
[ 356 ] 
