Measuring degradation of transgenic DNA and screening for horizontal gene transfer from GMO-plant material during composting

Summary in the original language of the document

The experiments show that composting of GM plant residues greatly increases the rate of degradation of transgenic DNA compared to the rate for plant residues left in the soil. If the persistence of transgenic DNA in the environments is considered as the only risk factor, composting is a 'DNA-safe' method to treat GM plant residues. However, even though transgenic plant DNA was not detected in bacterial isolates in our experiments, we cannot conclude that horizontal gene transfer can not take place. The 300 isolates tested proved to be too low a number to be conclusive. The numbers of isolates tested were based on the screenings indicating high transfer, but the screenings were biased apparently because some Bacillus species gave PCR products matching the transgenic DNA. Thus, it is still an open question if composting constitutes a safe way of disposing of GM plant residues. Furthermore, these experiments give rise to other interesting questions, e.g., the behavior of GM plant materials decomposing in waste piles or manure yards under composting-like conditions and the possibility of horizontal gene transfer to indigenous bacteria at the comparably lower temperatures presentat these environments.These questions need to be assessed if the risk associated with the use of GM plants is to be thoroughly investigated.