Genetic Engineering of Microorganisms: Free Release into the Environment

Genetic engineering now makes possible the insertion of DNA from many organisms into other prokaryotic, eukaryotic and viral hosts. This technology has been used to construct a variety of such genetically engineered microorganisms (GEMs). The possibility of accidental or deliberate release of GEMs into the natural environment has recently raised much public concern. The prospect of deliberate release of these microorganisms has prompted an increased need to understand the processes of survival, expression, transfer and rearrangement of recombinant DNA molecules in microbial communities. The methodology which is being developed to investigate these processes will greatly enhance our ability to study microbial population ecology. Once release has occurred, it is generally accepted that recovery of these cells from the natural environment can not be performed. Detecting their presence is the most that one can expect to achieve. Considerable effort in the construction of GEMs was initially placed on creating both microorganisms and cloning systems (plasmids used in the creation of recombinant DNA) that were considered "safe". These measures were designed to ensure that accidentally released strains would not survive or transfer their "novel" genetic material in the environment. The safeguards included debilitated host bacteria and cloning vectors, incapable of replication or transfer except under defined laboratory conditions. Such biological disabilities were used in conjunction with strict physical containment standards to reduce the likelihood of GEMs entering the environment. Since no hazardous consequences from work with recombinant DNA have been reported such safeguards are considered to have been successful. However, since an accident of this nature could have resulted in very subtle changes, this statement may only reflect our lack of understanding of the environment. Unlike accidental release it is impractical to disable GEMs that are designed for deliberate release. Strains are currently being constructed to survive at least for a limited time in specific target environments. Survival, to allow completion of their intended function, is essential for the application of most of these strains.