Planned Introduction of Genetically Engineered Microorganisms - GEMs - There is some data availble from field research using GEMs. The GEMs that are used live in the environment include bioremediation agents that degrade chemical waste. Immunoflurescence techniques have revealed a much higher survival of microbes than was previously suggested by the conventional techniques.

Therefore, it has been advocated that GEMs should be construced that contain active biological containment systems that minimize their survival and dissemination and or prevent the dissemination of recombinant DNA outside the target area. An example of such a biologically contained GEM is provided by Pseudomonas putida engineered to degrade alkyl benzoates.

2. The lacI repressor, in turn, binds promoter Plac and prevents transcription of the gef gene linked to it. Therefore, in the presence of 3MB, transcription of the gef gene is repressed; as a result, Gef protein is not produced, and the P. putida cells survive normally as long as 3MB is available to them.

3. However, when 3MB is not available to a cell, the xylS activator protein remains inactive. As a result, the regulator gene lad is not transcribed and lad repressor is not produced.

4. In the absence of lad repressor, gef gene (driven by Plac promoter) is expressed, and Gef protein is produced. Gef causes collapse of the membrane potential, which leads to cell death. Therefore, the cells of this genetically engineered P. putida strain commit suicide as soon as 3MB is exhaused and becomes unavailable to them; this minimizes their survival in the environment after they have degraded the alkylbenzoates present in the environment.