HORIZONTAL GENE-TRANSFER AS A BIOSAFETY ISSUE - A NATURAL PHENOMENON OF PUBLIC CONCERN

The transfer of genetic information between distantly or even unrelate d organisms during evolution had been inferred from nucleotide sequenc e comparisons. These studies provided circumstantial evidence that in rare cases genes had been laterally transmitted amongst organisms of t he domains bacteria, archaea and eukarya. Laboratory-based studies con firmed that the gene pools of the various domains of organisms are lin ked. Amongst the bacterial gene exchange mechanisms transduction, tran sformation and conjugation, the latter was identified as the mechanism with potentially the broadest host range of transfer. Previously, the issue of horizontal gene transfer has become important in the context of biosafety. Gene transfer studies carried out under more natural co nditions such as in model ecosystems or in the environment established that all gene transfer mechanisms worked under these conditions. More over, environmental hot-spots were identified where favourable conditi ons such as nutrient enrichment increased the probability of genetic e xchange among bacteria. In particular, the phytosphere was shown to pr ovide conducive conditions for conjugative gene exchange. Concern has been expressed that transfer of recombinant DNA (e.g. antibiotic resis tance genes) from genetically modified organisms (GMOs) such as transg enic plants to phytosphere bacteria may occur and thus contribute to t he undesirable spread of antibiotic resistance determinants. Studies w hich were performed to address this issue clearly showed that such a t ransfer occurs, if at all, at extremely low frequency. (C) 1998 Elsevi er Science B.V. All rights reserved.