Abstract: The environmental applications of genetically engineered microorganisms(GEMs) may cause many safety problems, It's necessary to assess the possible impacts of their planned release on ecosystems, with emphasis on the potential of horizontal transfer of artificially introduced genes between GEMs and indigenous microflora. and other ecologically important parameters like survival, dissemination and competition. It's also important to search for more valid methods of detection and to improve the strategy of risk assessment. The study is helpful for development of molecular ecology and application of biotechnology.

Key words: Molecular ecology, GEMs, Planned release, Risk assessment, rainfall, meteorological factors, dew amount, loess hilly region