Evaluation of the biorisk on the use of microorganisms for bioremediation in the environment

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For the accurate assessment of biorisk on the use of microorganisms including genetically engineered microorganisms (GEMs) for the bioremediation of polluted soil/aquatic environment, scientific information was accumulated and systemized through experimental investigations and model simulations.In the first year, biorisks on the horizontal transfer of the genes derived from exogenously introduced microorganisms to the indigenous harmful microorganisms such as pathogens were focused and investigated the factors which decide the frequency of the horizontal gene transfer as follows using model microcosm systems : 1.Survival of the GEMs introduced into natural environment, 2.Existence of the transmissible plasmids which have potential to transfer genetically engineered DNA sequences(GEDS), 3.Frequency and factors of plasmid transfer. The results were as follows : 1.GEMs introduced into soil and aquatic microcosms immediately decreased mainly because of the competition with indigenous micro … More organisms but after that survived at low level for relatively long periods, 2.There existed a certain level of microorganisms possessing tra gene, and therefore, the ability to transfer GEDS in natural environment, 3.GEDS could be transferred to wide range of indigenous microorganisms. These results implied that the GEDS can be transferred to indigenous microorganisms when GEMs possessing GEDS are released into the environment. The frame of the model to explain the behavior of the GEDS was also developed.In the second year, 1.The transferability of the GEDS by conjugation, 2.The influence of the various environmental factors on the frequency of the transfer were evaluated in detail using soil microcosms, and 3.The behavior of the GEDS was analyzed by model. Furthermore, 4.The behavior of exogenously introduced microorganisms and the influence on indigenous microbial community were evaluated at the real bioremediation fields. The results were as follows : 1.The possibility of the conjugative gene transfer was considerably lower in the soil environments than under the optimal laboratory condition, 2.The frequency of the transfer was influenced by the levels of the organic carbons, metals, and water contents, 3.The behavior of GEDS by conjugative transfer could be expressed by the modified mass action model, and 4.The exogenously introduced microorganisms decreased rapidly and no adverse effects were observed during bioremediation of real crude oil and dioxin contaminated soils. Less