K-12 has a limited potential of survival and their consensus that this bacterium 
cannot be converted into an epidemic pathogen by laboratory manipulations with 
DNA .inserts, has done much to satisfy the first concern mentioned above. As 
recently reported in the literature, (Petrocheilou, V., and Richmond, M. H. 
(1977) results from long-term monitoring of laboratory workers who routinely 
handled K-12 organisms carrying transmission-proficient plasmids showed no bowel 
colonization despite the fact that the work was carried out without any special 
precautions. If the organisms which carry recombinant DNA cannot spread in the 
natural environment, then clearly the other concerns must also be diminished. 
The conclusion of a NIH/EMBO Animal Virus Workshop (in Ascot, Jan. 1978) was 
that recombinant organisms carrying viral inserts cannot be any more hazardous 
than the viruses themselves, and in some instances may provide an opportunity to 
work more safely with virulent agents. 
As indicated in our report and in the proceedings of this meeting, important 
information on the nature and possible consequences of the manipulations used in 
recombinant DNA technology comes from experiments in a variety of fields. For 
example, attempts to understand the biological role of restriction enzymes have 
revealed that prokaryotic and eukaryotic DNAs can recombine in vivo . Other 
studies, including those with Agrobacterium tumef aciens and plant cells, also 
show that in some cases there is no barrier to exchange and expression of genes 
across the hypothetical prokaryotic-eukaryotic barrier. On the other hand, 
studies of animal virus genomes and eukaryotic genes for differentiated functions 
have revealed previously unsuspected possible barriers to their expression in 
prokaryotic backgrounds. It is clear that further studies of the molecular 
genetics, pathogenicity, ecology and other properties of organisms will continue 
to provide information relevant to the assessment of risk and that this source 
is no less important than specifically targeted experiments. 
Replies to our Questionnaire indicated that there were several projects underway 
directed specifically towards risk assessment. These included the two separate 
polyoma virus experiments sponsored by EMBO and by NIH and several NIH contracts 
aimed at testing and verification of EK2 and EK3 systems. Preliminary results, 
as well as conclusions from the NIH-EMBO Virology Workshop indicated that these 
studies were unlikely to reveal unknown hazards. However, these and other experi- 
ments aimed at elucidating various aspects of the ecology and natural history of 
microorganisms should provide useful information and will be important in the 
development of host-vector systems other than those based on Eh coli K-12. 
In summary, as of July 1978 our analyses had revealed no scientific findings to 
justify any of the three concerns listed above; no risk unique to recombinant 
DNA research was identified. Available evidence indicated that recombinations 
of the type made possible by this new technology could occur in Nature. Evalua- 
tion of Eh coli K-12 showed that this bacterium is essentially harmless and that 
insertions of segments of foreign DNA into its genome could not alter this 
property. With few exceptions, it seemed likely that the same would prove true 
of other host bacteria. 
Some of the results discussed in our report were also documented in material 
which accompanied publication of the December 1978 version of the U.S. NIH 
Guidelines. This material was included as part of the justification for relaxa- 
tion in containment requirements for permissible experiments. 
With respect to the second objective of our Working Group, at the time of our 
first report it appeared that additional information on results from feeding 
experiments and monitoring for acquistion of laboratory Eh coli strains would 
be useful. In these efforts we were fortunate in being able to enlist the aid 
of three distinguished investigators, Drs. S. Falkow (Seattle), Dr. M. Richmond 
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