Use of wide host range promoters to monitor the fate of recombinant DNA in soil

Abstract

The release of microorganisms obtained by recombinant DNA techniques is considered to improve their beneficial performance in crop production, nitrogen fixation, biodegradation of environmental pollutants or as biological pesticides1 and the first field tests with genetically engineered microorganisms (GEMs) have recently been made.2 The risk assessment of such projects may involve many factors, reflecting the complexity of environmental interactions. It needs to consider possible changes in the fitness of the GEM with respect to the target microflora, to evaluate how such GEMs survive, affect the environment and exchange genetic material with native members of the soil microflora. It is generally agreed that the potential ecological risk of any GEM introduction has to be assessed case by case.3,4 One major focus in risk assessment is the possible in situ transfer or recombinant DNA among microbes. Information on gene transfer in soil is scarce, in spite of considerable knowledge gathered with in vitro mating systems. To investigate genetic exchanges in the natural environment genes coding for an antibiotic resistance are often used to monitor survival and distribution of GEMs and its DNA via selection. Although DNA transfer was shown to occur in the environment among introduced organisms5–10 conjugation or mobilization of plasmids from GEMs to the resident soil microflora has not been demonstrated in situ yet. Possibly transfer rates were below the limit of detection.