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(32-03) Genetically engineered microorganisms in the terrestrial ecosystems: Monitoring techniques and risk assessments . Tebbe, Christoph*,1, 1 Institut fuer Agraroekologie, Braunschweig, Germany ABSTRACT- With the upcoming concern about potential environmental risks of genetically enginnered microorganisms (GMO) since the beginning of the 1980's it became evident, that there was a tremendous lack of methods to be able to follow the fate of GMO in soil and potential interactions with their abiotic and biotic environment. First results on GMO studies in soil under laboratory conditions indicated mostely different rates of decline of GMO in bulk soil. However, such studies did not adequately reflect the heterogeneity and diversity of microbial habitats which exist in terrestrial ecosystems. In our own studies in context of risk evaluations of GMO in soil we therefore included the analysis of specific microbial niches in soil, with an emphasis to rhizospheres and the gut and faeces of soil invertebrates. We could demonstrate that conjugative gene transfer between bacteria can be enhanced by the activity of Collembola (spring tails) and in earthworms. In context of the first field release with genetically engineered bacteria in Germany, which was conducted in collaboration with Alfred Puehler and Mathias Keller (University of Bielefeld), we found that field inoculated rhizobia (Sinorhizobium meliloti) can colonize rhizospheres of alfalfa and transiently replace indigenous bacteria. The bacterial strains, inoculated in 1995 onto a field site at our research centre in Braunschweig, can still be detected today, even though the populations sizes now are relatively small (102 g-1 soil) and indigenous rhizobia continuously outcompete the GMO. Currently, we investigate strategies with which established GMO can be removed from soil. In the frame of greenhouse and field studies we compare the efficiency of various methods, such as crop rotation, use of agro-chemicals and wild-type inoculations. Our field site in Braunschweig is the only site in Germany and, next to Rothemstedt England, the only site in Europe, to our knowledge, which allows to conduct long-term monitoring of GMO under field conditions. The futher monitoring of these sites will provide useful data to evaluate the biosafety of future bacterial inoculants for agricultural applications. Key words: soil microbiology, risk assessment, genetically engineered organisms, genetically modified organisms |
