Gene/biotechnology and the broad use of genetically modified organisms is rapidly developing into a commercial enterprise. In spite of the pace of scientific progress in this field, a partly emotional debate is still being carried on by the general public and on the part of the consumer about the potential risks linked to this new technology. Especially when genetically modified organisms (GMOs) are tested in the open field, the question of "safety" is controversially discussed among different groups in society. Environmentalists are worried about unforeseeable dangers inherent in the release of a living organism, assuming that special risks are linked to organisms which have been modified by molecular biologists using tools developed in the laboratory. Frequently quoted potential hazards are the phenomena of "gene escape" and "genetic pollution", meaning the very interesting question of natural (horizontal) gene transfer. This phenomenon of horizontal gene transfer is in fact well known to scientists studying prokaryotes. Many prokaryotes are able to exchange DNA readily between individuals of different species or are even able to take up DNA from the extracellular environment by the process of genetic transformation, which has already been known for more than 65 years. For eukaryotes, however, the evidence of natural horizontal gene transfer is very limited.