Risks associated with the application of genetically modified microorganisms in terrestrial ecosystems

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Abstract
The application of genetically modified microorganisms (GEMMOs) in agriculture has great possibilities. However, the lack of knowledge on the occurrence of unwanted effects on the soil ecosystem still prevents the large-scale use of GEMMOs. Moreover, experimental work in risk assessment does not always fit the guidelines presented by regulatory agencies. To provide a framework as a basis for both risk assessment research and regulatory agencies for decisions on releases, a flow scheme is presented containing key processes controlling bacterial fate and thus putative risk. It is suggested that the fate of the GEMMO has to be investigated at first in contained microcosms mimicking the environment in comparison to the wild-type organism. Inoculant survival, competition, gene transfer and translocation are key parameters to be investigated in case of a wanted release. As a general rule, the GEMMO should not be fitter than the wild-type, which might result in displacement of this species. Moreover, GEMMO transport should not be different from the wild-type. Also, transfer of the heterologous element should not occur to a great extent. Localization of the genetic element in the genome is a key factor affecting gene transfer. The most difficult point to address is the possible effect of the GEMMO on ecosystem functioning and diversity. Many different parameters, each giving specific information about the ecosystem, can be investigated. From a regulatory point of view it is important to provide researchers in risk assessment with a basic set of parameters to be studied; guidelines concerning acceptability of effects must also be provided. The application of biological containment methods, such as via the use of inducible killing genes, will put a time limit on the possible hazard of GEMMO introductions. Although biological containment methods do not (yet) completely eliminate introduced GEMMOs, their further development will be an important factor for allowing future field experiments.

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